Subject: Moveing the geophone inside
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 06 Jan 2007 07:49:20 +0000
Hi all and a Happy New year 2007.
After few months of testing I have dedicated to move my geophone back
inside. It works to have the geophone outside, but the problem is that I
don't have a quiet enugh location for it, since the garden where I live
is open and pepole often alomost run on top of the geophone.My remote
stations setups are all going to be above the ground, so not burrying
the geophone is going to be a standard for me.
Bye.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Geophone with long legs
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 06 Jan 2007 13:19:50 +0000
Hi all
I am wondering, since I did move my geophone back inside, is the
geophone less sensitive becose he now stands on the legs but is not
surrounded in sand like when I did have him outside. Does it matter in
the terms of detecting earthquakes ?
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Geophone with long legs
From: Dave Nelson davenn@...............
Date: Sun, 07 Jan 2007 09:10:43 +1100
yes Jon
it MUST be in good contact with the ground to record ground motion=
properly.
if it is just sitting on the floor of the house or as sounds like, on=20
legs above the floor
then most of anything it will record will be house/floor movement.
if it must be brought closer to the house, then either bury it under the=
=20
house if there is underfloor access. if ur house is on a concrete pad then=
=20
its going to have to go outside beside the house.
Either way its still going to record a lot of building movement and=20
movement of people from within the house
cheers
Dave N
Sydney, Oz
At 01:19 PM 6/01/2007 +0000, you wrote:
>Hi all
>
>I am wondering, since I did move my geophone back inside, is the
>geophone less sensitive becose he now stands on the legs but is not
>surrounded in sand like when I did have him outside. Does it matter in
>the terms of detecting earthquakes ?
>
>Regards.
>--
>J=F3n Fr=EDmann
>http://www.jonfr.com
>http://www.simnet.is/jonfr500/earthquake/
>
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with
>the body of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: 6/01/2007=
=20
>7:47 PM
>
>
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: 6/01/2007=
=20
>7:47 PM
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: 6/01/2007 7:=
47 PM
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: Geophone with long legs
From: "Timothy Carpenter" geodynamics@.......
Date: Sat, 6 Jan 2007 18:35:55 -0500
Jon,
Dave is correct, you must have good contact with the ground (or at least =
the
floor) in order to get the optimal readings. Just standing on the legs =
is
not a good installation.
If you can unscrew the spikes (legs) then remove them. In that case, =
place
the geophone on the floor and put a 5 to 10kg sandbag on top of it. (An =
good
alternative would be to glue the geophone to the floor -- but that's
probably not acceptable.) Either sandbagging or gluing will give =
reasonably
good coupling and will minimize the chances of it getting bumped out of
place. The next best alternative is to use your plastic bucket. Bury the
geophone in dry sand in the bucket and place it in a out-of-the-way =
location
(remember to mark your north-south axis).
Regards,
-Tim-
Timothy Carpenter, P.E., Pres.
GeoDynamics Consultants, Inc.
5043 Whitlow Court
Commerce Township, Michigan 48382
248-363-4529 (Voice & Fax)
248-766-1629 (Cell)
geodynamics@........... (primary)
geodynamics@....... (secondary)
-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
On
Behalf Of Dave Nelson
Sent: Saturday, January 06, 2007 5:11 PM
To: psn-l@..............
Subject: Re: Geophone with long legs
yes Jon
it MUST be in good contact with the ground to record ground motion
properly.
if it is just sitting on the floor of the house or as sounds like, =
on=20
legs above the floor
then most of anything it will record will be house/floor movement.
if it must be brought closer to the house, then either bury it under =
the=20
house if there is underfloor access. if ur house is on a concrete pad =
then=20
its going to have to go outside beside the house.
Either way its still going to record a lot of building movement and=20
movement of people from within the house
cheers
Dave N
Sydney, Oz
At 01:19 PM 6/01/2007 +0000, you wrote:
>Hi all
>
>I am wondering, since I did move my geophone back inside, is the
>geophone less sensitive becose he now stands on the legs but is not
>surrounded in sand like when I did have him outside. Does it matter in
>the terms of detecting earthquakes ?
>
>Regards.
>--
>J=F3n Fr=EDmann
>http://www.jonfr.com
>http://www.simnet.is/jonfr500/earthquake/
>
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with
>the body of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: =
6/01/2007=20
>7:47 PM
>
>
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: =
6/01/2007=20
>7:47 PM
--=20
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: =
6/01/2007
7:47 PM
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: Geophone with long legs
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sun, 07 Jan 2007 09:59:32 +0000
Hi
I was able to remove the spikes with some help, since they where really
rusted and stuck. Based on the noise level, the pickup appears to be
normal, but I won't really see it until I get a earthquake and this week
it has been quiet. But I have only recored one earthquake this week (I
now use week system, week 1, week 2 etc.). I see no reasion to use a
sandbag to increase the load, I do have a bucked on top of it for
isolation purposes.
This setup is going to be a standard for every one of my stations that I
plan to setup. But this year I will setup a remote station in a diffrent
town that is nearly 80 km away from me (I think). The first one out of
at least three ones.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Filters
From: "tchannel" tchannel@..............
Date: Sun, 7 Jan 2007 07:21:30 -0700
Hi Folks, One issue where I seem to need help, is how to filter. I =
have keep notes on the Low and High Pass filter values used by others.
I also know that the filter values will change with all the variables. =
Let us assume, using a vertical similar to the AS1, what would be good =
starting points for Local, Regional, and Teleseimetic events? Also =
could someone explain what the poles numbers do?
Thanks, Ted
Hi Folks, One issue where I seem =
to need=20
help, is how to filter. I have keep notes on the Low and High Pass =
filter=20
values used by others.
I also know that the filter values will =
change with=20
all the variables. Let us assume, using a vertical similar =
to the=20
AS1, what would be good starting points for Local, Regional, and =
Teleseimetic=20
events? Also could someone explain what the poles numbers=20
do?
Thanks, Ted
Subject: Re: Filters
From: ChrisAtUpw@.......
Date: Sun, 7 Jan 2007 22:19:51 EST
In a message dated 07/01/2007, tchannel@.............. writes:
Hi Folks, One issue where I seem to need help, is how to filter. I have
keep notes on the Low and High Pass filter values used by others.
I also know that the filter values will change with all the variables. Let
us assume, using a vertical similar to the AS1, what would be good starting
points for Local, Regional, and Teleseismic events?
Hi Ted,
If you are using an AS-1, the sample rate is set to 6 sps, so the max
frequency that can be detected is 3 Hz. You have no choice.
However, if you are using a Lehman, you might wish to set the low pass
at 20 Hz for Local / Volcanic events, 10 Hz for Regional events or 5 Hz for
Teleseismic events. The high pass filter should be set at or a bit above the
set period of the sensor - lower in frequency.
But you are usually presented with an amplifier with built in frequency
/ period values. The filters are used to remove man made / environmental
noise, which is usually serious at frequencies of 20 Hz and above and VLF 1/f
noise.
Also could someone explain what the poles numbers do?
The corner frequency is set by the capacitor values. Increasing the
number of poles (stages) increases the cut-off slope by 6 dB per octave per pole
above the corner frequency and this also requires an increase in the number
of opamps. It is usual to assign two poles (RC stages) per opamp. However,
each stage adds to the signal delay through the filter. A five or six stage
filter is usually adequate.
Bessel filters have a constant delay over the passband and this figure
may be entered into the SDR program to compensate. The signal 'shape' is
fairly well maintained. Butterworth filters have a large peak delay at the edge of
the passband and the signal 'shape' may be seriously distorted if any
frequency component is near the edge of the passband.
Regards,
Chris Chapman
In a message dated 07/01/2007, tchannel@.............. writes:
Hi Folks, One issue where I seem to=
need=20
help, is how to filter. I have keep notes on the Low and High Pass filter=20
values used by others.
I also know that the filter values will c=
hange=20
with all the variables. Let us assume, using a vertical similar to t=
he=20
AS1, what would be good starting points for Local, Regional, and Teleseism=
ic=20
events?
Hi Ted,
If you are using an AS-1, the sample rate is se=
t to=20
6 sps, so the max frequency that can be detected is 3 Hz. You have no=20
choice.
However, if you are using a Lehman, you might w=
ish=20
to set the low pass at 20 Hz for Local / Volcanic events, 10 Hz for Regional=
=20
events or 5 Hz for Teleseismic events. The high pass filter should be set at=
or=20
a bit above the set period of the sensor - lower in frequency.
But you are usually presented with an amplifier=
=20
with built in frequency / period values. The filters are used to remove=
man=20
made / environmental noise, which is usually serious at frequencies of =
20=20
Hz and above and VLF 1/f noise.
Also could someone explain what the p=
oles=20
numbers do?
The corner frequency is set by the capacitor=20
values. Increasing the number of poles (stages) increases the cut-off slope=20=
by 6=20
dB per octave per pole above the corner frequency and this also requires=20
an increase in the number of opamps. It is usual=20
to assign two poles (RC stages) per opamp. However, each stage add=
s to=20
the signal delay through the filter. A five or six stage filter is usually=20
adequate.
Bessel filters have a constant delay over the=20
passband and this figure may be entered into the SDR program to compensate.=20=
The=20
signal 'shape' is fairly well maintained. Butterworth filters have a la=
rge=20
peak delay at the edge of the passband and the signal 'shape' may be serious=
ly=20
distorted if any frequency component is near the edge of the passband.
Regards,
Chris Chapman
Subject: Rockland filter
From: Bob Barns royb1@...........
Date: Mon, 08 Jan 2007 10:07:36 -0500
For great flexibility, sharp cut-off, etc., I think that the Rockland
analog filters are the way to go. With this type of adjustable filter,
you can easily try different settings to see which is best for you. I
have a Rockland model 1022F-04.
It is dual channel. The two channels can be independently set.
Function:low or high pass, response is Butterworth or RC, attenuation
slope is 24 db/oct [this is really sharp], there are several models:
model cut-off range
01 0.01Hz to 111kHz
02 0.001Hz to 11.1 kHz
03 0.1Hz to 111 kHz
04 0.01 Hz to 11.1 kHz
input is single ended, 10M impedence
gain is 0db or 20 db
Output is single ended 50 ohms impedence
If you want only a single filter, the two sections can be connected in
series to provide REALLY sharp cut-off or a band-pass filter.
It is rack mount, 5 1/4" hi, 17" wide and 14" deep and weighs 18 lbs.
Power consumption is less than 10W
I can supply a photocopy of the manual.
There us currently a digital Rockland on ebay but it looks expensive and
I don't know the specs. The analog version comes up occasionaly.
I paid <$200 several years ago on ebay.
Bob
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Rockland filter
From: ChrisAtUpw@.......
Date: Mon, 8 Jan 2007 12:16:00 EST
In a message dated 08/01/2007, royb1@........... writes:
There us currently a digital Rockland on ebay but it looks expensive and
I don't know the specs. The analog version comes up occasionaly.
Hi Bob,
I haven't read the data manual for a Rockland Digital Filter, but the
problem with digital filters for seismic use has previously been their low
dynamic range. They are simply too noisy and may give less than 80 dB, where over
120 dB would be desirable.
Regards,
Chris Chapman
In a message dated 08/01/2007, royb1@........... writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>There us=20
currently a digital Rockland on ebay but it looks expensive and I don'=
t=20
know the specs. The analog version comes up=20
occasionaly.
Hi Bob,
I haven't read the data manual for a Rockl=
and=20
Digital Filter, but the problem with digital filters for seismic use has=20
previously been their low dynamic range. They are simply too noisy and=20=
may=20
give less than 80 dB, where over 120 dB would be desirable.
Regards,
Chris Chapman
Subject: Re: Rockland filter
From: "Dewayne" n0ssy@...........
Date: Mon, 8 Jan 2007 11:19:22 -0700
I have a Rockland analog filter I purchased at a Ham radio fest many years
ago. If someone would like to purchase it, make an offer.
As I do not have any packaging I will take it to a package/shipping store.
This cost would be added to your offer. If I get multiple
offers the highest will be considered.
E-mail me directly at: n0ssy@...........
Dewayne
----- Original Message -----
From: "Bob Barns"
To: "psn mail"
Sent: Monday, January 08, 2007 8:07 AM
Subject: Rockland filter
> For great flexibility, sharp cut-off, etc., I think that the Rockland
> analog filters are the way to go. With this type of adjustable filter, you
> can easily try different settings to see which is best for you. I have a
> Rockland model 1022F-04.
> It is dual channel. The two channels can be independently set.
> Function:low or high pass, response is Butterworth or RC, attenuation
> slope is 24 db/oct [this is really sharp], there are several models:
> model cut-off range
> 01 0.01Hz to 111kHz
> 02 0.001Hz to 11.1 kHz
> 03 0.1Hz to 111 kHz
> 04 0.01 Hz to 11.1 kHz
> input is single ended, 10M impedence
> gain is 0db or 20 db
> Output is single ended 50 ohms impedence
>
> If you want only a single filter, the two sections can be connected in
> series to provide REALLY sharp cut-off or a band-pass filter.
>
> It is rack mount, 5 1/4" hi, 17" wide and 14" deep and weighs 18 lbs.
> Power consumption is less than 10W
> I can supply a photocopy of the manual.
>
> There us currently a digital Rockland on ebay but it looks expensive and I
> don't know the specs. The analog version comes up occasionaly.
> I paid <$200 several years ago on ebay.
>
>
>
> Bob
>
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with the body of the
> message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: 150th Anniversary of forgotten quake
From: JD Cooley jdcooley@.......
Date: Mon, 08 Jan 2007 16:50:44 -0800
http://news.yahoo.com/s/ap/20070108/ap_on_re_us/forgotten_quake_1
Subject: Re: Filters
From: Bobhelenmcclure@.......
Date: Mon, 8 Jan 2007 21:04:02 EST
Ted (tchannel) wrote:
Hi Folks, One issue where I seem to need help, is how to filter. I have
kept notes on the Low and High Pass filter values used by others. I also know
that the filter values will change with all the variables. Let us assume,
using a vertical similar to the AS1, what would be good starting points for
Local, Regional, and Teleseimetic events? Also could someone explain what the
poles numbers do?
Hi Ted,
The object of seismic filtering is to reproduce the signal with as little
distortion as possible and attenuate the noise. In the case of seismic
signals, the spectrum containing the signal is dependent on event distance, and the
noise is primarily from microseisms and cultural noise, including traffic,
other human activity, and wind. Microseisms range widely in intensity and
frequency. Their period ranges primarily from 2 seconds to 7 seconds. Cultural
noise, in my experience, is generally short period and can be easily rejected
except for local events, which also have a short period. Wind, by exerting
pressure on trees and structures, imparts long period motion to the ground, and
can for the most part be excluded by long period high pass filtering. The same
applies to tilt induced by walking anywhere near a horizontal sensor.
Usually, the sensor itself is the high pass filter. Amplifier bias drift and 1/f
noise are also long period effects. Atmospheric pressure and temperature
changes cause the pendulum to drift.
For intermediate distance and long distance events, microseisms are right
in the frequency range of interest, and you probably should just suffer them.
My advice on filtering is to let experience be your guide, but use the
best filters you can, and do as little filtering as you can get away with. In my
opinion, the lowpass and highpass filters in WinQuake stink, and I have
developed my own filters. They are implemented in my WQFilter.exe utility
program, and anyone can download and try them out on WinQuake files. The approach I
use is to broadbrand the signal first with my period extending filter
(especially necessary with the AS1), and then restrict the high and low ends of the
frequency range with Butterworth filters. You should restrict the number of
poles used. The number of poles determines the steepness of the rolloff at the
corner frequency. However, more poles means more ringing in the filter
impulse response, which you do not want.
You can learn a lot about filters by downloading "seismic_dataq.zip" from
John Lahr's web site. Extract "WQFilter.exe", "WQFilterHlp.txt", and
"Impulse.psn" from the zip. Use both WinQuake and WQFilter to filter "Impulse.psn" with
the various filters of each program. Using WinQuake, examine the resulting
filtered response (the impulse response). The FFT of the impulse response will
give you the passband spectrum of the filter. The impulse response itself
will tell you about the group time delay and ringing response of the filter. My
filters have zero time delay and phase distortion. This is achieved by
filtering the data forward in time, and then backward in time (impossible to do
with an analog filter).
This is the Digital Age. Analog is dead! Do not listen to anyone about
analog filter circuits. Analog filtering has no place anymore except at the
front end of the A/D converter, and even that need is minimized by sampling at a
high rate and subsequently downsampling with maybe some digital filtering
thrown in.
Bob
Ted (tchannel) wrote: Hi Folks, One issue where I seem to need=
=20
help, is how to filter. I have kept notes on the Low and High Pass fil=
ter=20
values used by others. I also know that the filter values will change with a=
ll=20
the variables. Let us assume, using a vertical similar to the AS1, what woul=
d be=20
good starting points for Local, Regional, and Teleseimetic events? &nbs=
p;=20
Also could someone explain what the poles numbers do?
Hi Ted,
The object of seismic filtering is to reproduce the signal with=20=
as=20
little distortion as possible and attenuate the noise. In the case of seismi=
c=20
signals, the spectrum containing the signal is dependent on event distance,=20=
and=20
the noise is primarily from microseisms and cultural noise, including traffi=
c,=20
other human activity, and wind. Microseisms range widely in intensity and=20
frequency. Their period ranges primarily from 2 seconds to 7 seconds. Cultur=
al=20
noise, in my experience, is generally short period and can be easily rejecte=
d=20
except for local events, which also have a short period. Wind, by exerting=20
pressure on trees and structures, imparts long period motion to the ground,=20=
and=20
can for the most part be excluded by long period high pass filtering. The sa=
me=20
applies to tilt induced by walking anywhere near a horizontal sensor. Usuall=
y,=20
the sensor itself is the high pass filter. Amplifier bias drift and 1/f nois=
e=20
are also long period effects. Atmospheric pressure and temperature changes c=
ause=20
the pendulum to drift.
For intermediate distance and long distance events, microseisms=20=
are=20
right in the frequency range of interest, and you probably should just suffe=
r=20
them.
My advice on filtering is to let experience be your guide, but u=
se=20
the best filters you can, and do as little filtering as you can get away wit=
h.=20
In my opinion, the lowpass and highpass filters in WinQuake stink, and I hav=
e=20
developed my own filters. They are implemented in my WQFilter.exe utility=20
program, and anyone can download and try them out on WinQuake files. The=20
approach I use is to broadbrand the signal first with my period extendi=
ng=20
filter (especially necessary with the AS1), and then restrict the high and l=
ow=20
ends of the frequency range with Butterworth filters. You should restrict th=
e=20
number of poles used. The number of poles determines the steepness of the=20
rolloff at the corner frequency. However, more poles means more ringing in t=
he=20
filter impulse response, which you do not want.
You can learn a lot about filters by downloading "seismic_dataq.zip" fr=
om=20
John Lahr's web site. Extract "WQFilter.exe", "WQFilterHlp.txt", and=20
"Impulse.psn" from the zip. Use both WinQuake and WQFilter to filter=20
"Impulse.psn" with the various filters of each program. Using WinQuake, exam=
ine=20
the resulting filtered response (the impulse response). The FFT of the impul=
se=20
response will give you the passband spectrum of the filter. The impulse resp=
onse=20
itself will tell you about the group time delay and ringing response of the=20
filter. My filters have zero time delay and phase distortion. This is achiev=
ed=20
by filtering the data forward in time, and then backward in time (impossible=
to=20
do with an analog filter).
This is the Digital Age. Analog is dead! Do not listen to anyone=
=20
about analog filter circuits. Analog filtering has no place anymore except a=
t=20
the front end of the A/D converter, and even that need is minimized by sampl=
ing=20
at a high rate and subsequently downsampling with maybe some digital filteri=
ng=20
thrown in.
Bob
Subject: Re: Filters
From: "tchannel" tchannel@..............
Date: Mon, 8 Jan 2007 20:48:38 -0700
Hi Folks, Just wanted to thank everyone for their most excellent help =
on this subject. Ted
----- Original Message -----=20
From: Bobhelenmcclure@..........
To: psn-l@.................
Sent: Monday, January 08, 2007 7:04 PM
Subject: Re: Filters
Ted (tchannel) wrote:
Hi Folks, One issue where I seem to need help, is how to filter. I =
have kept notes on the Low and High Pass filter values used by others. I =
also know that the filter values will change with all the variables. Let =
us assume, using a vertical similar to the AS1, what would be good =
starting points for Local, Regional, and Teleseimetic events? Also =
could someone explain what the poles numbers do?=20
Hi Ted,
The object of seismic filtering is to reproduce the signal with as =
little distortion as possible and attenuate the noise. In the case of =
seismic signals, the spectrum containing the signal is dependent on =
event distance, and the noise is primarily from microseisms and cultural =
noise, including traffic, other human activity, and wind. Microseisms =
range widely in intensity and frequency. Their period ranges primarily =
from 2 seconds to 7 seconds. Cultural noise, in my experience, is =
generally short period and can be easily rejected except for local =
events, which also have a short period. Wind, by exerting pressure on =
trees and structures, imparts long period motion to the ground, and can =
for the most part be excluded by long period high pass filtering. The =
same applies to tilt induced by walking anywhere near a horizontal =
sensor. Usually, the sensor itself is the high pass filter. Amplifier =
bias drift and 1/f noise are also long period effects. Atmospheric =
pressure and temperature changes cause the pendulum to drift.
For intermediate distance and long distance events, microseisms are =
right in the frequency range of interest, and you probably should just =
suffer them.
My advice on filtering is to let experience be your guide, but use =
the best filters you can, and do as little filtering as you can get away =
with. In my opinion, the lowpass and highpass filters in WinQuake stink, =
and I have developed my own filters. They are implemented in my =
WQFilter.exe utility program, and anyone can download and try them out =
on WinQuake files. The approach I use is to broadbrand the signal first =
with my period extending filter (especially necessary with the AS1), and =
then restrict the high and low ends of the frequency range with =
Butterworth filters. You should restrict the number of poles used. The =
number of poles determines the steepness of the rolloff at the corner =
frequency. However, more poles means more ringing in the filter impulse =
response, which you do not want.=20
You can learn a lot about filters by downloading "seismic_dataq.zip" =
from John Lahr's web site. Extract "WQFilter.exe", "WQFilterHlp.txt", =
and "Impulse.psn" from the zip. Use both WinQuake and WQFilter to filter =
"Impulse.psn" with the various filters of each program. Using WinQuake, =
examine the resulting filtered response (the impulse response). The FFT =
of the impulse response will give you the passband spectrum of the =
filter. The impulse response itself will tell you about the group time =
delay and ringing response of the filter. My filters have zero time =
delay and phase distortion. This is achieved by filtering the data =
forward in time, and then backward in time (impossible to do with an =
analog filter).=20
This is the Digital Age. Analog is dead! Do not listen to anyone =
about analog filter circuits. Analog filtering has no place anymore =
except at the front end of the A/D converter, and even that need is =
minimized by sampling at a high rate and subsequently downsampling with =
maybe some digital filtering thrown in.
Bob
Hi Folks, Just wanted to thank everyone for their most =
excellent help=20
on this subject. Ted
Ted (tchannel) wrote: Hi Folks, One issue where I seem =
to need=20
help, is how to filter. I have kept notes on the Low and High =
Pass=20
filter values used by others. I also know that the filter values will =
change=20
with all the variables. Let us assume, using a vertical similar to the =
AS1,=20
what would be good starting points for Local, Regional, and =
Teleseimetic=20
events? Also could someone explain what the poles numbers =
do?=20
Hi Ted,
The object of seismic filtering is to reproduce the signal =
with as=20
little distortion as possible and attenuate the noise. In the case of =
seismic=20
signals, the spectrum containing the signal is dependent on event =
distance,=20
and the noise is primarily from microseisms and cultural noise, =
including=20
traffic, other human activity, and wind. Microseisms range widely in =
intensity=20
and frequency. Their period ranges primarily from 2 seconds to 7 =
seconds.=20
Cultural noise, in my experience, is generally short period and can be =
easily=20
rejected except for local events, which also have a short period. =
Wind, by=20
exerting pressure on trees and structures, imparts long period motion =
to the=20
ground, and can for the most part be excluded by long period high pass =
filtering. The same applies to tilt induced by walking anywhere near a =
horizontal sensor. Usually, the sensor itself is the high pass filter. =
Amplifier bias drift and 1/f noise are also long period effects. =
Atmospheric=20
pressure and temperature changes cause the pendulum to drift.
For intermediate distance and long distance events, =
microseisms=20
are right in the frequency range of interest, and you probably should =
just=20
suffer them.
My advice on filtering is to let experience be your guide, =
but use=20
the best filters you can, and do as little filtering as you can get =
away with.=20
In my opinion, the lowpass and highpass filters in WinQuake stink, and =
I have=20
developed my own filters. They are implemented in my WQFilter.exe =
utility=20
program, and anyone can download and try them out on WinQuake files. =
The=20
approach I use is to broadbrand the signal first with my period =
extending=20
filter (especially necessary with the AS1), and then restrict the high =
and low=20
ends of the frequency range with Butterworth filters. You should =
restrict the=20
number of poles used. The number of poles determines the steepness of =
the=20
rolloff at the corner frequency. However, more poles means more =
ringing in the=20
filter impulse response, which you do not want.
You can learn a lot about filters by downloading =
"seismic_dataq.zip" from=20
John Lahr's web site. Extract "WQFilter.exe", "WQFilterHlp.txt", and=20
"Impulse.psn" from the zip. Use both WinQuake and WQFilter to filter=20
"Impulse.psn" with the various filters of each program. Using =
WinQuake,=20
examine the resulting filtered response (the impulse response). The =
FFT of the=20
impulse response will give you the passband spectrum of the filter. =
The=20
impulse response itself will tell you about the group time delay and =
ringing=20
response of the filter. My filters have zero time delay and phase =
distortion.=20
This is achieved by filtering the data forward in time, and then =
backward in=20
time (impossible to do with an analog filter).
This is the Digital Age. Analog is dead! Do not listen to =
anyone=20
about analog filter circuits. Analog filtering has no place anymore =
except at=20
the front end of the A/D converter, and even that need is minimized by =
sampling at a high rate and subsequently downsampling with maybe some =
digital=20
filtering thrown in.
Bob
Subject: Re: Filters
From: "Dewayne" n0ssy@...........
Date: Mon, 8 Jan 2007 21:06:17 -0700
Bob , If analog is dead would you please tell me where I can find a 120v =
to 12v digital transformer. LOL
Dewayne
----- Original Message -----=20
From: Bobhelenmcclure@..........
To: psn-l@.................
Sent: Monday, January 08, 2007 7:04 PM
Subject: Re: Filters
Ted (tchannel) wrote:
Hi Folks, One issue where I seem to need help, is how to filter. I =
have kept notes on the Low and High Pass filter values used by others. I =
also know that the filter values will change with all the variables. Let =
us assume, using a vertical similar to the AS1, what would be good =
starting points for Local, Regional, and Teleseimetic events? Also =
could someone explain what the poles numbers do?=20
Hi Ted,
The object of seismic filtering is to reproduce the signal with as =
little distortion as possible and attenuate the noise. In the case of =
seismic signals, the spectrum containing the signal is dependent on =
event distance, and the noise is primarily from microseisms and cultural =
noise, including traffic, other human activity, and wind. Microseisms =
range widely in intensity and frequency. Their period ranges primarily =
from 2 seconds to 7 seconds. Cultural noise, in my experience, is =
generally short period and can be easily rejected except for local =
events, which also have a short period. Wind, by exerting pressure on =
trees and structures, imparts long period motion to the ground, and can =
for the most part be excluded by long period high pass filtering. The =
same applies to tilt induced by walking anywhere near a horizontal =
sensor. Usually, the sensor itself is the high pass filter. Amplifier =
bias drift and 1/f noise are also long period effects. Atmospheric =
pressure and temperature changes cause the pendulum to drift.
For intermediate distance and long distance events, microseisms are =
right in the frequency range of interest, and you probably should just =
suffer them.
My advice on filtering is to let experience be your guide, but use =
the best filters you can, and do as little filtering as you can get away =
with. In my opinion, the lowpass and highpass filters in WinQuake stink, =
and I have developed my own filters. They are implemented in my =
WQFilter.exe utility program, and anyone can download and try them out =
on WinQuake files. The approach I use is to broadbrand the signal first =
with my period extending filter (especially necessary with the AS1), and =
then restrict the high and low ends of the frequency range with =
Butterworth filters. You should restrict the number of poles used. The =
number of poles determines the steepness of the rolloff at the corner =
frequency. However, more poles means more ringing in the filter impulse =
response, which you do not want.=20
You can learn a lot about filters by downloading "seismic_dataq.zip" =
from John Lahr's web site. Extract "WQFilter.exe", "WQFilterHlp.txt", =
and "Impulse.psn" from the zip. Use both WinQuake and WQFilter to filter =
"Impulse.psn" with the various filters of each program. Using WinQuake, =
examine the resulting filtered response (the impulse response). The FFT =
of the impulse response will give you the passband spectrum of the =
filter. The impulse response itself will tell you about the group time =
delay and ringing response of the filter. My filters have zero time =
delay and phase distortion. This is achieved by filtering the data =
forward in time, and then backward in time (impossible to do with an =
analog filter).=20
This is the Digital Age. Analog is dead! Do not listen to anyone =
about analog filter circuits. Analog filtering has no place anymore =
except at the front end of the A/D converter, and even that need is =
minimized by sampling at a high rate and subsequently downsampling with =
maybe some digital filtering thrown in.
Bob
Bob , If analog is dead would you please tell me where I can find a =
120v to=20
12v digital transformer. LOL
Ted (tchannel) wrote: Hi Folks, One issue where I seem =
to need=20
help, is how to filter. I have kept notes on the Low and High =
Pass=20
filter values used by others. I also know that the filter values will =
change=20
with all the variables. Let us assume, using a vertical similar to the =
AS1,=20
what would be good starting points for Local, Regional, and =
Teleseimetic=20
events? Also could someone explain what the poles numbers =
do?=20
Hi Ted,
The object of seismic filtering is to reproduce the signal =
with as=20
little distortion as possible and attenuate the noise. In the case of =
seismic=20
signals, the spectrum containing the signal is dependent on event =
distance,=20
and the noise is primarily from microseisms and cultural noise, =
including=20
traffic, other human activity, and wind. Microseisms range widely in =
intensity=20
and frequency. Their period ranges primarily from 2 seconds to 7 =
seconds.=20
Cultural noise, in my experience, is generally short period and can be =
easily=20
rejected except for local events, which also have a short period. =
Wind, by=20
exerting pressure on trees and structures, imparts long period motion =
to the=20
ground, and can for the most part be excluded by long period high pass =
filtering. The same applies to tilt induced by walking anywhere near a =
horizontal sensor. Usually, the sensor itself is the high pass filter. =
Amplifier bias drift and 1/f noise are also long period effects. =
Atmospheric=20
pressure and temperature changes cause the pendulum to drift.
For intermediate distance and long distance events, =
microseisms=20
are right in the frequency range of interest, and you probably should =
just=20
suffer them.
My advice on filtering is to let experience be your guide, =
but use=20
the best filters you can, and do as little filtering as you can get =
away with.=20
In my opinion, the lowpass and highpass filters in WinQuake stink, and =
I have=20
developed my own filters. They are implemented in my WQFilter.exe =
utility=20
program, and anyone can download and try them out on WinQuake files. =
The=20
approach I use is to broadbrand the signal first with my period =
extending=20
filter (especially necessary with the AS1), and then restrict the high =
and low=20
ends of the frequency range with Butterworth filters. You should =
restrict the=20
number of poles used. The number of poles determines the steepness of =
the=20
rolloff at the corner frequency. However, more poles means more =
ringing in the=20
filter impulse response, which you do not want.
You can learn a lot about filters by downloading =
"seismic_dataq.zip" from=20
John Lahr's web site. Extract "WQFilter.exe", "WQFilterHlp.txt", and=20
"Impulse.psn" from the zip. Use both WinQuake and WQFilter to filter=20
"Impulse.psn" with the various filters of each program. Using =
WinQuake,=20
examine the resulting filtered response (the impulse response). The =
FFT of the=20
impulse response will give you the passband spectrum of the filter. =
The=20
impulse response itself will tell you about the group time delay and =
ringing=20
response of the filter. My filters have zero time delay and phase =
distortion.=20
This is achieved by filtering the data forward in time, and then =
backward in=20
time (impossible to do with an analog filter).
This is the Digital Age. Analog is dead! Do not listen to =
anyone=20
about analog filter circuits. Analog filtering has no place anymore =
except at=20
the front end of the A/D converter, and even that need is minimized by =
sampling at a high rate and subsequently downsampling with maybe some =
digital=20
filtering thrown in.
Bob
Subject: Re: Filters
From: ChrisAtUpw@.......
Date: Mon, 8 Jan 2007 23:49:07 EST
In a message dated 09/01/2007, Bobhelenmcclure@....... writes:
This is the Digital Age. Analog is dead! Do not listen to anyone about
analog filter circuits. Analog filtering has no place anymore except at the front
end of the A/D converter, and even that need is minimized by sampling at a
high rate and subsequently downsampling with maybe some digital filtering
thrown in.
Nonsence!
Chris
In a message dated 09/01/2007, Bobhelenmcclure@....... writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>This is=20
the Digital Age. Analog is dead! Do not listen to anyone about analog filt=
er=20
circuits. Analog filtering has no place anymore except at the front end of=
the=20
A/D converter, and even that need is minimized by sampling at a high rate=20=
and=20
subsequently downsampling with maybe some digital filtering thrown=20
in.
Nonsence!
Chris
Subject: Re: Geophone with long legs
From: "Geoffrey" gmvoeth@...........
Date: Mon, 8 Jan 2007 22:50:25 -0700
I have often thought it would right
to cut a hole in the slab and drill down a few
feet then set the geophone on a post that
has been driven a foot or two into the ground
at that location but the post must be isolated
from the slab as well as the surrounding hole.
I have seen vibration isolation slabs in
microciruit manufacturing labs
so that their photo whatever will
stay as still as possible.
----- Original Message -----
From: "Dave Nelson"
To:
Sent: Saturday, January 06, 2007 3:10 PM
Subject: Re: Geophone with long legs
yes Jon
it MUST be in good contact with the ground to record ground motion properly.
if it is just sitting on the floor of the house or as sounds like, on
legs above the floor
then most of anything it will record will be house/floor movement.
if it must be brought closer to the house, then either bury it under the
house if there is underfloor access. if ur house is on a concrete pad then
its going to have to go outside beside the house.
Either way its still going to record a lot of building movement and
movement of people from within the house
cheers
Dave N
Sydney, Oz
At 01:19 PM 6/01/2007 +0000, you wrote:
>Hi all
>
>I am wondering, since I did move my geophone back inside, is the
>geophone less sensitive becose he now stands on the legs but is not
>surrounded in sand like when I did have him outside. Does it matter in
>the terms of detecting earthquakes ?
>
>Regards.
>--
>Jón Frímann
>http://www.jonfr.com
>http://www.simnet.is/jonfr500/earthquake/
>
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with
>the body of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: 6/01/2007 7:47 PM
>
>
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: 6/01/2007 7:47 PM
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.16.7/618 - Release Date: 6/01/2007 7:47 PM
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Filters
From: "Geoffrey" gmvoeth@...........
Date: Mon, 8 Jan 2007 22:55:02 -0700
One thing you did not mention is phase distortion when you filter ???
I should imagine that phase distortions will
cause the original waveform to be mishapen
when it is read by the A/D
converter and I know of no way to stop this from happening.
It is good that most seismic phase signals stay
inside a relatively narrow range.
----- Original Message -----
From:
To:
Sent: Monday, January 08, 2007 7:04 PM
Subject: Re: Filters
> Ted (tchannel) wrote:
> Hi Folks, One issue where I seem to need help, is how to filter. I have
> kept notes on the Low and High Pass filter values used by others. I also know
> that the filter values will change with all the variables. Let us assume,
> using a vertical similar to the AS1, what would be good starting points for
> Local, Regional, and Teleseimetic events? Also could someone explain what the
> poles numbers do?
>
> Hi Ted,
>
> The object of seismic filtering is to reproduce the signal with as little
> distortion as possible and attenuate the noise. In the case of seismic
> signals, the spectrum containing the signal is dependent on event distance, and the
> noise is primarily from microseisms and cultural noise, including traffic,
> other human activity, and wind. Microseisms range widely in intensity and
> frequency. Their period ranges primarily from 2 seconds to 7 seconds. Cultural
> noise, in my experience, is generally short period and can be easily rejected
> except for local events, which also have a short period. Wind, by exerting
> pressure on trees and structures, imparts long period motion to the ground, and
> can for the most part be excluded by long period high pass filtering. The same
> applies to tilt induced by walking anywhere near a horizontal sensor.
> Usually, the sensor itself is the high pass filter. Amplifier bias drift and 1/f
> noise are also long period effects. Atmospheric pressure and temperature
> changes cause the pendulum to drift.
>
> For intermediate distance and long distance events, microseisms are right
> in the frequency range of interest, and you probably should just suffer them.
>
> My advice on filtering is to let experience be your guide, but use the
> best filters you can, and do as little filtering as you can get away with. In my
> opinion, the lowpass and highpass filters in WinQuake stink, and I have
> developed my own filters. They are implemented in my WQFilter.exe utility
> program, and anyone can download and try them out on WinQuake files. The approach I
> use is to broadbrand the signal first with my period extending filter
> (especially necessary with the AS1), and then restrict the high and low ends of the
> frequency range with Butterworth filters. You should restrict the number of
> poles used. The number of poles determines the steepness of the rolloff at the
> corner frequency. However, more poles means more ringing in the filter
> impulse response, which you do not want.
>
> You can learn a lot about filters by downloading "seismic_dataq.zip" from
> John Lahr's web site. Extract "WQFilter.exe", "WQFilterHlp.txt", and
> "Impulse.psn" from the zip. Use both WinQuake and WQFilter to filter "Impulse.psn" with
> the various filters of each program. Using WinQuake, examine the resulting
> filtered response (the impulse response). The FFT of the impulse response will
> give you the passband spectrum of the filter. The impulse response itself
> will tell you about the group time delay and ringing response of the filter. My
> filters have zero time delay and phase distortion. This is achieved by
> filtering the data forward in time, and then backward in time (impossible to do
> with an analog filter).
>
> This is the Digital Age. Analog is dead! Do not listen to anyone about
> analog filter circuits. Analog filtering has no place anymore except at the
> front end of the A/D converter, and even that need is minimized by sampling at a
> high rate and subsequently downsampling with maybe some digital filtering
> thrown in.
>
> Bob
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Geophone with long legs
From: "Geoffrey" gmvoeth@...........
Date: Mon, 8 Jan 2007 23:04:53 -0700
The whole earth in the location of
the geophone should move in unison
so I think that is not the issue.
It is a matter of signal to noise ratio
and since the slab rides upon the ground like a ship in the ocean
I think it to be very important to put the geophone
directly on the ocean (ground) and not on any slab
that has other activity upon it.
I use an alarm to record my files and since
relocating underground and a few feet from the slab my false alarms are few. You should fix somehow your geophone to the ground
so that in the event of motions that exceed 1g (32f/s^2
things will not be destroyed. Greater than 1G and your
geophone will hop like a kaninchen out of its rightful place.
A whole firetruck has been known to do this and if a person
had been next to it thay might have been crushed to death.
Those trucks may have 2000 gallons of water at 8.1Avodupoise
pounds per gallon.
----- Original Message -----
From: "Jón Frímann"
To: "PSN-Postlist"
Sent: Saturday, January 06, 2007 6:19 AM
Subject: Geophone with long legs
> Hi all
>
> I am wondering, since I did move my geophone back inside, is the
> geophone less sensitive becose he now stands on the legs but is not
> surrounded in sand like when I did have him outside. Does it matter in
> the terms of detecting earthquakes ?
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Rockland filter
From: Bob Barns royb1@...........
Date: Tue, 09 Jan 2007 11:11:20 -0500
With the usual 14 or 16 bit A/D's, is that dynamic range necessary?
Bob
ChrisAtUpw@....... wrote:
> In a message dated 08/01/2007, royb1@........... writes:
>
> There us currently a digital Rockland on ebay but it looks
> expensive and
> I don't know the specs. The analog version comes up occasionaly.
>
> Hi Bob,
>
> I haven't read the data manual for a Rockland Digital Filter, but
> the problem with digital filters for seismic use has previously been
> their low dynamic range. They are simply too noisy and may give less
> than 80 dB, where over 120 dB would be desirable.
>
> Regards,
>
> Chris Chapman
>
>
> __________ NOD32 1966 (20070109) Information __________
>
> This message was checked by NOD32 antivirus system.
> http://www.eset.com
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Reading a Seismogram
From: "tchannel" tchannel@..............
Date: Tue, 9 Jan 2007 18:50:13 -0700
Hi Folks, These questions may have to do with art and experience, as =
much as science. Can one explain how to read a Seismogram, if that is =
the correct word? That is the enlarged section of the recorded trace. =
I normally can find the P and S. I also understand the different =
directional movements, as illustrated in pictures I have seen.=20
1. Are the large waves that follow the S, surface waves?
2. If so can one discern Loves from Rayleigh's, within that section?
3. Do the Loves and Rayleigh's arrive at different times, as with P and =
S? and or, do the look different?
I am sure the more you work with these recordings the better you can =
interpret them.
A related question: I just recorded a very nice image of the 5.7m =
01/09/2007 Southeastern Alaska 2259km from Boise Idaho, using my =
Vertical Spring sensor. The best recording, so far, using this new =
sensor. I was please with the image; a clear P, a smaller but clear S, =
followed by a large series of waves, I assume, to be surface waves. But =
here I can't tell a Love from a Rayleigh. =20
I did not know a vertical spring sensor would pick up surface waves, =
even though the Rayleigh's could move the vertical spring. Is it that =
the vertical is less likely to pick up these waves at greater distances, =
because of their longer periods?
Thanks, Ted
Hi Folks, These questions may =
have to do with=20
art and experience, as much as science. Can one explain how to =
read a=20
Seismogram, if that is the correct word? That is the enlarged =
section of=20
the recorded trace. I normally can find the P and S. I also =
understand=20
the different directional movements, as illustrated in pictures I =
have=20
seen.
1. Are the large waves that =
follow the=20
S, surface waves?
2. If so can one discern Loves =
from=20
Rayleigh's, within that section?
3. Do the Loves and Rayleigh's =
arrive at=20
different times, as with P and S? and or, do the look=20
different?
I am sure the more you work with these =
recordings=20
the better you can interpret them.
A related question: I just =
recorded a very=20
nice image of the 5.7m 01/09/2007 Southeastern Alaska 2259km from Boise =
Idaho,=20
using my Vertical Spring sensor. The best recording, so far, =
using=20
this new sensor. I was please with the image; a clear P, a =
smaller=20
but clear S, followed by a large series of waves, I assume, to be =
surface=20
waves. But here I can't tell a Love from a Rayleigh. =
I did not know a vertical spring sensor =
would pick=20
up surface waves, even though the Rayleigh's could move the=20
vertical spring. Is it that the vertical is less likely to =
pick up=20
these waves at greater distances, because of their longer =
periods?
Thanks, Ted
Subject: Re: Reading a Seismogram
From: ChrisAtUpw@.......
Date: Tue, 9 Jan 2007 21:51:02 EST
In a message dated 10/01/2007, tchannel@.............. writes:
Hi Folks, These questions may have to do with art and experience, as much=20
as science. Can one explain how to read a Seismogram, if that is the corre=
ct=20
word? That is the enlarged section of the recorded trace. I normally can=20
find the P and S. I also understand the different directional movements, as=
=20
illustrated in pictures I have seen.=20
Hi Ted,
=20
I suggest that you download and print a copy of the seismic time travel=
=20
graph from _http://neic.usgs.gov/neis/travel_times/ttgraph.html_=20
(http://neic.usgs.gov/neis/travel_times/ttgraph.html) =20
=20
When an earthquake occurs, two types of wave are generated. The faster=20
compression P waves have their displacement in the direction of propagation=
..=20
The slower S shear waves have their displacement perpendicular to their=20
direction of propagation. Local frequency components up to a few hundred Hz=
may be=20
recorded, but these =E2=80=98high frequency=E2=80=99 components are rapidly=
absorbed as the=20
signals travel through the Earth.=20
When these waves reach the surface of the Earth, they generate slower=20
surface waves, which propagate radially outwards. The Love waves have the h=
igher=20
velocity and their displacement is perpendicular to the direction of=20
propagation in the plane of the surface. The Rayleigh waves are slower and=20=
have a=20
retrograde vertical motion in the direction of propagation.
The wave propagation is constrained by the transmission velocities in the=20
various Earth layers, the crust, the mantle and the cores. I suggest that=20=
you=20
download the seismograph training manual from=20
_http://psn.quake.net/info/analysis.pdf_ (http://psn.quake.net/info/analysis=
..pdf) Due to layering and the=20
curvature of the Earth, the seismic responses are divided into local (0 to=20
1.4 deg), near regional (1.4 to 6 deg.), regional (6 to 16 deg.) and=20
teleseismic responses (16 to 180 deg.). The angle is that between the sour=
ce and the=20
observer at the centre of the Earth. See p 12. A 1 degree angle correspond=
s=20
to 111.3 km, 69.2 miles or 60 nautical mile at the surface.
The P and S waves have frequencies between 0.5 and maybe 40 Hz, with the S=20
waves having a bit less than =C2=BD the period of the associated P waves. P=
waves=20
from regional and teleseismic events may have frequencies between 1 and 3 H=
z.=20
The L and R surface waves may have periods up to several hundred seconds=20
depending on the physical dimensions of the seismic slip, but for smaller q=
uakes=20
they are more typically between 10 and 30 seconds. The amplitude of Rayleig=
h=20
waves of about 20 sec period are often measured to determine the magnitude=20=
of=20
a quake. For Local and Near Regional quakes, the amplitudes of the P or S=20
waves may be used to determine the quake magnitude.
Visual seismic displays are described at=20
_http://www.geol.binghamton.edu/faculty/jones/_ (http://www.geol.binghamton.=
edu/faculty/jones/)=20
download seisvole.readme and download the program SeismicEruptionSetup.exe
While the surface waves radiate outwards in a fairly simple and predictable=
=20
manner, the waves within the earth generate new wave pairs at every=20
refraction and reflection. The response to a large quake depends on the dep=
th of the=20
quake as well as the angle between it and the observer and can get very =20
complicated.
1. Are the large waves that follow the S, surface waves?
Yes, but see the time travel graph
2. If so can one discern Loves from Rayleigh's, within that section?
The Love waves have the higher velocity and are horizontally polarised.
The Rayleigh waves are a bit slower and are vertically polarised.
3. Do the Loves and Rayleigh's arrive at different times, as with P and S?=
=20
and or, do the look different?
=20
I am sure the more you work with these recordings the better you can=20
interpret them.
=20
A related question: I just recorded a very nice image of the 5.7m 01/09/200=
7=20
Southeastern Alaska 2259km from Boise Idaho, using my Vertical Spring=20
sensor. The best recording, so far, using this new sensor. I was please wi=
th the=20
image; a clear P, a smaller but clear S, followed by a large series of wave=
s,=20
I assume, to be surface waves. But here I can't tell a Love from a Rayleig=
h.
Note that the surface waves are polarised. A vertical sensor will pick=20
up mostly Rayleigh waves. A Lehman will pick up mostly Love waves
I did not know a vertical spring sensor would pick up surface waves, eve=
n=20
though the Rayleigh's could move the vertical spring. Is it that the =20
vertical is less likely to pick up these waves at greater distances, because=
of=20
their longer periods?
A sensor will still react to motions at less than it's resonant period,=
=20
but the amplitude of the response decreases with the square of the ratio of=
=20
the resonant period to the wave period. So if your vertical sensor has a=20
period of 2 secs, a typical Rayleigh wave of 20 seconds will show about 1/1=
00 the=20
'normal' sensitivity.
=20
Regards,
=20
Chris Chapman
In a message dated 10/01/2007, tchannel@.............. writes:
Hi Folks, These questions may have=20=
to do=20
with art and experience, as much as science. Can one explain how to=20=
read=20
a Seismogram, if that is the correct word? That is the enlarged sect=
ion=20
of the recorded trace. I normally can find the P and S. I also=20
understand the different directional movements, as illustrated in=20
pictures I have seen.
Hi Ted,
I suggest that you download and print a copy of=
the=20
seismic time travel graph from http://neic.usg=
s.gov/neis/travel_times/ttgraph.html
When an earthquake occurs, two types of wave ar=
e=20
generated. The faster compression P waves have their displacement in the=20
direction of propagation. The slower S shear waves have their displacement=20
perpendicular to their direction of propagation. Local frequency components=20=
up=20
to a few hundred Hz may be recorded, but these =E2=80=98high frequency=E2=
=80=99 components are=20
rapidly absorbed as the signals travel through the=20
Earth. When these waves reach the surface o=
f=20
the Earth, they generate slower surface waves, which propagate radially=20
outwards. The Love waves have the higher velocity and their displacement is=20
perpendicular to the direction of propagation in the plane of the surface. T=
he=20
Rayleigh waves are slower and have a retrograde vertical motion in the direc=
tion=20
of propagation. The wave propagation is constrain=
ed=20
by the transmission velocities in the various Earth layers, the crust, the=20
mantle and the cores. I suggest that you download the seismograph trai=
ning=20
manual from http://psn.quake.net/info/an=
alysis.pdf =20
Due to layering and the curvature of the Earth, the seismic responses are=20
divided into local (0 to 1.4 deg), near regional (1.4 to 6 deg.), regional (=
6 to=20
16 deg.) and teleseismic responses (16 to 180 deg.). The angle is that=
=20
between the source and the observer at the centre of the Earth. See p 12.&nb=
sp;=20
A 1 degree angle corresponds to 111.3 km, 69.2 miles or 60 nautical mile at=20=
the=20
surface. The P and S waves have frequencies betwe=
en=20
0.5 and maybe 40 Hz, with the S waves having a bit less than =C2=BD the peri=
od of the=20
associated P waves. P waves from regional and teleseismic events may have=20
frequencies between 1 and 3 Hz. The L and R surface waves may have periods u=
p to=20
several hundred seconds depending on the physical dimensions of the seismic=20
slip, but for smaller quakes they are more typically between 10 and 30 secon=
ds.=20
The amplitude of Rayleigh waves of about 20 sec period are often measured to=
=20
determine the magnitude of a quake. For Local and Near Regional quakes, the=20
amplitudes of the P or S waves may be used to determine the quake=20
magnitude. Visual seismic displays are described at http://www.geol.bingh=
amton.edu/faculty/jones/
download seisvole.readme and download the=20
program SeismicEruptionSetup.exe While the=20
surface waves radiate outwards in a fairly simple and predictable manner, th=
e=20
waves within the earth generate new wave pairs at every refraction and=20
reflection. The response to a large quake depends on the depth of the quake=20=
as=20
well as the angle between it and the observer and can get very=20
complicated.
3. Do the Loves and Rayleigh's arri=
ve at=20
different times, as with P and S? and or, do the look=20
different?
I am sure the more you work with these re=
cordings=20
the better you can interpret them.
A related question: I just recorded=20=
a very=20
nice image of the 5.7m 01/09/2007 Southeastern Alaska 2259km from Boise Id=
aho,=20
using my Vertical Spring sensor. The best recording, so far, using t=
his=20
new sensor. I was please with the image; a clear P, a smaller but clear S,=
=20
followed by a large series of waves, I assume, to be surface waves.=20=
But=20
here I can't tell a Love from a Rayleigh.
Note that the surface waves are polarised. A=20
vertical sensor will pick up mostly Rayleigh waves. A Lehman will pick up mo=
stly=20
Love waves
I=20
did not know a vertical spring sensor would pick up surface waves, even th=
ough=20
the Rayleigh's could move the vertical spring. Is it that the=20
vertical is less likely to pick up these waves at greater distances, becau=
se=20
of their longer periods?
A sensor will still react to motions at less th=
an=20
it's resonant period, but the amplitude of the response decreases with the=20
square of the ratio of the resonant period to the wave period. So if your=20
vertical sensor has a period of 2 secs, a typical Rayleigh wave of 20 second=
s=20
will show about 1/100 the 'normal' sensitivity.
Regards,
Chris Chapman
Subject: Re: Rockland filter
From: ChrisAtUpw@.......
Date: Tue, 9 Jan 2007 21:58:00 EST
In a message dated 09/01/2007 16:16:40 GMT Standard Time, royb1@...........
writes:
With the usual 14 or 16 bit A/D's, is that dynamic range necessary?
Bob
Hi Bob,
A 16 bit ADC with no noise has +/-1/2 bit uncertainty. This is about 96
dB. Each factor of 2 gives 6 dB change. With +/-10V input 1 bit = 0.305 mV
Quiet opamps may give 0.1 to 10 Hz input noise levels well below 1 micro
volt; true chopper amplifiers may be much less than this. The CAZ opamps
tend to give 1 to 2 micro volts, but these may give OK results for long period
signals, when 1/f drifts become large. It is a good principle to use odd
orders of low pass filter with a capacitor across the feedback resistor of the
first opamp. Never amplify high frequency signals. This limits the effect of
intermodulation distortion and subharmonics
Digital filters tend to give performance in the mid 70 dBs, or less, but
also suffer from switch transient feed through - 5 mV? - which may need
additional analogue filtering before putting it into an ADC.
In seismometry, we are seeking very low noise levels at very low
frequencies. You just can't afford to throw away +/-4 bits signal through a poor
choice of filter, or +/-3 bits by failing to average out the internal ADC noise.
While you can increase the amplifier gain to display small signals over
internal noise, a reduction of the range by a factor of 8 or more is very
undesirable.
Your available dynamic range is usually far less than the maximum range
of signals that you can receive.
If you use a Lehman or similar long period sensor, you should set your
background microseism signal to maybe 200 counts. If you don't do this, you
may not be able to sense the long period low amplitude signals masked by the
microseism background.
Regards,
Chris Chapman
In a message dated 09/01/2007 16:16:40 GMT Standard Time, royb1@comcast=
..net=20
writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>With the=20
usual 14 or 16 bit A/D's, is that dynamic range=20
necessary? Bob
Hi Bob,
A 16 bit ADC with no noise has +/-1/2 bit=20
uncertainty. This is about 96 dB. Each factor of 2 gives 6 dB change. With=20
+/-10V input 1 bit =3D 0.305 mV
Quiet opamps may give 0.1 to 10 Hz input noise=20
levels well below 1 micro volt; true chopper amplifiers may be much less tha=
n=20
this. The CAZ opamps tend to give 1 to 2 micro volts, but these may give OK=20
results for long period signals, when 1/f drifts become large. It is a good=20
principle to use odd orders of low pass filter with a capacitor across the=20
feedback resistor of the first opamp. Never amplify high frequency signals.=20=
This=20
limits the effect of intermodulation distortion and subharmonics
Digital filters tend to give performance in the=
mid=20
70 dBs, or less, but also suffer from switch transient feed through - 5 mV?=20=
-=20
which may need additional analogue filtering before putting it into an=20
ADC.
In seismometry, we are seeking very low noise=20
levels at very low frequencies. You just can't afford to throw away +/-4 bit=
s=20
signal through a poor choice of filter, or +/-3 bits by failing to average o=
ut=20
the internal ADC noise. While you can increase the amplifier gain to=20
display small signals over internal noise, a reduction of the range by a fac=
tor=20
of 8 or more is very undesirable.
Your available dynamic range is usually far=20=
less=20
than the maximum range of signals that you can receive.
If you use a Lehman or similar long period sens=
or,=20
you should set your background microseism signal to maybe 200 counts. If you=
=20
don't do this, you may not be able to sense the long period low amplitude=20
signals masked by the microseism background.
Regards,
Chris Chapman
Subject: Re: Reading a Seismogram
From: "tchannel" tchannel@..............
Date: Wed, 10 Jan 2007 10:22:35 -0700
Hi Chris, Thanks again! Extremely well written and very useful reply. =
Linda my wife, an English major, worked as an report specialist and =
editor for 31 years, working with scientific publications.......She will =
also enjoy reading this.
Cheers, Ted
----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Tuesday, January 09, 2007 7:51 PM
Subject: Re: Reading a Seismogram
In a message dated 10/01/2007, tchannel@.............. writes:
Hi Folks, These questions may have to do with art and experience, =
as much as science. Can one explain how to read a Seismogram, if that =
is the correct word? That is the enlarged section of the recorded =
trace. I normally can find the P and S. I also understand the different =
directional movements, as illustrated in pictures I have seen.=20
Hi Ted,
I suggest that you download and print a copy of the seismic time =
travel graph from http://neic.usgs.gov/neis/travel_times/ttgraph.html=20
When an earthquake occurs, two types of wave are generated. The =
faster compression P waves have their displacement in the direction of =
propagation. The slower S shear waves have their displacement =
perpendicular to their direction of propagation. Local frequency =
components up to a few hundred Hz may be recorded, but these =
=E2=80=98high frequency=E2=80=99 components are rapidly absorbed as the =
signals travel through the Earth.=20
When these waves reach the surface of the Earth, they generate =
slower surface waves, which propagate radially outwards. The Love waves =
have the higher velocity and their displacement is perpendicular to the =
direction of propagation in the plane of the surface. The Rayleigh waves =
are slower and have a retrograde vertical motion in the direction of =
propagation.
The wave propagation is constrained by the transmission velocities =
in the various Earth layers, the crust, the mantle and the cores. I =
suggest that you download the seismograph training manual from =
http://psn.quake.net/info/analysis.pdf Due to layering and the =
curvature of the Earth, the seismic responses are divided into local (0 =
to 1.4 deg), near regional (1.4 to 6 deg.), regional (6 to 16 deg.) and =
teleseismic responses (16 to 180 deg.). The angle is that between the =
source and the observer at the centre of the Earth. See p 12. A 1 =
degree angle corresponds to 111.3 km, 69.2 miles or 60 nautical mile at =
the surface.
The P and S waves have frequencies between 0.5 and maybe 40 Hz, =
with the S waves having a bit less than =C2=BD the period of the =
associated P waves. P waves from regional and teleseismic events may =
have frequencies between 1 and 3 Hz. The L and R surface waves may have =
periods up to several hundred seconds depending on the physical =
dimensions of the seismic slip, but for smaller quakes they are more =
typically between 10 and 30 seconds. The amplitude of Rayleigh waves of =
about 20 sec period are often measured to determine the magnitude of a =
quake. For Local and Near Regional quakes, the amplitudes of the P or S =
waves may be used to determine the quake magnitude.
Visual seismic displays are described at =
http://www.geol.binghamton.edu/faculty/jones/
download seisvole.readme and download the program =
SeismicEruptionSetup.exe
While the surface waves radiate outwards in a fairly simple and =
predictable manner, the waves within the earth generate new wave pairs =
at every refraction and reflection. The response to a large quake =
depends on the depth of the quake as well as the angle between it and =
the observer and can get very complicated.
1. Are the large waves that follow the S, surface waves?
Yes, but see the time travel graph
2. If so can one discern Loves from Rayleigh's, within that =
section?
The Love waves have the higher velocity and are horizontally =
polarised.
The Rayleigh waves are a bit slower and are vertically polarised.
3. Do the Loves and Rayleigh's arrive at different times, as with P =
and S? and or, do the look different?
I am sure the more you work with these recordings the better you can =
interpret them.
A related question: I just recorded a very nice image of the 5.7m =
01/09/2007 Southeastern Alaska 2259km from Boise Idaho, using my =
Vertical Spring sensor. The best recording, so far, using this new =
sensor. I was please with the image; a clear P, a smaller but clear S, =
followed by a large series of waves, I assume, to be surface waves. But =
here I can't tell a Love from a Rayleigh.
Note that the surface waves are polarised. A vertical sensor will =
pick up mostly Rayleigh waves. A Lehman will pick up mostly Love waves
I did not know a vertical spring sensor would pick up surface =
waves, even though the Rayleigh's could move the vertical spring. Is it =
that the vertical is less likely to pick up these waves at greater =
distances, because of their longer periods?
A sensor will still react to motions at less than it's resonant =
period, but the amplitude of the response decreases with the square of =
the ratio of the resonant period to the wave period. So if your vertical =
sensor has a period of 2 secs, a typical Rayleigh wave of 20 seconds =
will show about 1/100 the 'normal' sensitivity.
Regards,
Chris Chapman
=EF=BB=BF
Hi Chris, Thanks again! Extremely well written =
and very=20
useful reply. Linda my wife, an English major, worked as an report =
specialist and editor for 31 years, working with scientific=20
publications.......She will also enjoy reading this.
In a message dated 10/01/2007, tchannel@..............=20
writes:
Hi Folks, These questions may =
have to do=20
with art and experience, as much as science. Can one explain =
how to=20
read a Seismogram, if that is the correct word? That is the =
enlarged=20
section of the recorded trace. I normally can find the P and =
S. I also=20
understand the different directional movements, as illustrated =
in=20
pictures I have seen.
Hi Ted,
I suggest that you download and print a =
copy of=20
the seismic time travel graph from http://neic.=
usgs.gov/neis/travel_times/ttgraph.html
When an earthquake occurs, two types of =
wave are=20
generated. The faster compression P waves have their displacement in =
the=20
direction of propagation. The slower S shear waves have their =
displacement=20
perpendicular to their direction of propagation. Local frequency =
components up=20
to a few hundred Hz may be recorded, but these =E2=80=98high =
frequency=E2=80=99 components are=20
rapidly absorbed as the signals travel through the=20
Earth. When these waves reach the =
surface of=20
the Earth, they generate slower surface waves, which propagate =
radially=20
outwards. The Love waves have the higher velocity and their =
displacement is=20
perpendicular to the direction of propagation in the plane of the =
surface. The=20
Rayleigh waves are slower and have a retrograde vertical motion in the =
direction of propagation. The wave =
propagation is=20
constrained by the transmission velocities in the various Earth =
layers, the=20
crust, the mantle and the cores. I suggest that you download the =
seismograph training manual from http://psn.quake.net/info=
/analysis.pdf =20
Due to layering and the curvature of the Earth, the seismic responses =
are=20
divided into local (0 to 1.4 deg), near regional (1.4 to 6 deg.), =
regional (6=20
to 16 deg.) and teleseismic responses (16 to 180 deg.). The =
angle is=20
that between the source and the observer at the centre of the Earth. =
See p=20
12. A 1 degree angle corresponds to 111.3 km, 69.2 miles or 60 =
nautical=20
mile at the surface. The P and S waves have =
frequencies between 0.5 and maybe 40 Hz, with the S waves having a bit =
less=20
than =C2=BD the period of the associated P waves. P waves from =
regional and=20
teleseismic events may have frequencies between 1 and 3 Hz. The L and =
R=20
surface waves may have periods up to several hundred seconds depending =
on the=20
physical dimensions of the seismic slip, but for smaller quakes they =
are more=20
typically between 10 and 30 seconds. The amplitude of Rayleigh waves =
of about=20
20 sec period are often measured to determine the magnitude of a =
quake. For=20
Local and Near Regional quakes, the amplitudes of the P or S waves may =
be used=20
to determine the quake magnitude. Visual seismic displays are =
described at http://www.geol.bi=
nghamton.edu/faculty/jones/
download seisvole.readme and download the=20
program SeismicEruptionSetup.exe While =
the=20
surface waves radiate outwards in a fairly simple and predictable =
manner, the=20
waves within the earth generate new wave pairs at every refraction and =
reflection. The response to a large quake depends on the depth of the =
quake as=20
well as the angle between it and the observer and can get very=20
complicated.
1. Are the large waves =
that follow=20
the S, surface waves?
Yes, but see the time travel graph
2. If so can one discern =
Loves from=20
Rayleigh's, within that section?
The Love waves have the higher velocity =
and are=20
horizontally polarised.
The Rayleigh waves are a bit slower and =
are=20
vertically polarised.
3. Do the Loves and =
Rayleigh's arrive at=20
different times, as with P and S? and or, do the look=20
different?
I am sure the more you work with =
these=20
recordings the better you can interpret them.
A related question: I just =
recorded a very=20
nice image of the 5.7m 01/09/2007 Southeastern Alaska 2259km from =
Boise=20
Idaho, using my Vertical Spring sensor. The best recording, so =
far,=20
using this new sensor. I was please with the image; a clear P, a =
smaller but=20
clear S, followed by a large series of waves, I assume, to be =
surface=20
waves. But here I can't tell a Love from a=20
Rayleigh.
Note that the surface waves are =
polarised. A=20
vertical sensor will pick up mostly Rayleigh waves. A Lehman will pick =
up=20
mostly Love waves
I=20
did not know a vertical spring sensor would pick up surface waves, =
even=20
though the Rayleigh's could move the vertical spring. Is =
it that=20
the vertical is less likely to pick up these waves at greater =
distances,=20
because of their longer periods?
A sensor will still react to motions at =
less than=20
it's resonant period, but the amplitude of the response decreases with =
the=20
square of the ratio of the resonant period to the wave period. So if =
your=20
vertical sensor has a period of 2 secs, a typical Rayleigh wave of 20 =
seconds=20
will show about 1/100 the 'normal' sensitivity.
Regards,
Chris=20
Chapman
Subject: Re: Reading a Seismogram
From: George Bush ke6pxp@.......
Date: Wed, 10 Jan 2007 09:46:41 -0800
Ted-
Larry Cochrane has provided some great tools right in Winquake. He allows
you to see the time of the various phases. To see these, set your P and S
times and than pull-down VIEW, select Phases and click the right button
and click DISPLAY and all of the phases of the various waves are
displayed as labelled red lines on your display. If I see some strong
waves on the graph while using WINQUAKE, I do this and try to understand
what is happening.
At 06:50 PM 1/9/2007 -0700, you wrote:
>>>>
Hi Folks, These questions may have to do with art and experience, as
much as science. Can one explain how to read a Seismogram, if that is
the correct word? That is the enlarged section of the recorded trace. I
normally can find the P and S. I also understand the different
directional movements, as illustrated in pictures I have seen.
1. Are the large waves that follow the S, surface waves?
2. If so can one discern Loves from Rayleigh's, within that section?
3. Do the Loves and Rayleigh's arrive at different times, as with P and
S? and or, do the look different?
I am sure the more you work with these recordings the better you can
interpret them.
A related question: I just recorded a very nice image of the 5.7m
01/09/2007 Southeastern Alaska 2259km from Boise Idaho, using my Vertical
Spring sensor. The best recording, so far, using this new sensor. I
was please with the image; a clear P, a smaller but clear S, followed by
a large series of waves, I assume, to be surface waves. But here I can't
tell a Love from a Rayleigh.
I did not know a vertical spring sensor would pick up surface waves, even
though the Rayleigh's could move the vertical spring. Is it that the
vertical is less likely to pick up these waves at greater distances,
because of their longer periods?
Thanks, Ted
<<<<<<<<
George
Subject: Wave Id's
From: "tchannel" tchannel@..............
Date: Thu, 11 Jan 2007 11:08:20 -0700
Hi All, It was pointed out that within Winquake software is a pulldown =
menu which places the various wave id markers. Is there a page avail =
which explains what the id's initials stand for? As an example P=3D =
primary S=3D secondary SSS,? LQ, LR and so on.
Thanks, Ted
Hi All, It was pointed out that =
within=20
Winquake software is a pulldown menu which places the various wave id=20
markers. Is there a page avail which explains what the id's =
initials stand=20
for? As an example P=3D primary S=3D secondary SSS,? LQ, LR =
and so=20
on.
Thanks, Ted
Subject: Earthquake swarm
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Thu, 11 Jan 2007 19:13:36 +0000
Hi all
Today around 17:23 UTC a earthquake swarm did start, this earthquake
swarm is about 150 km away from my location. Earthquake dection is from
good to poor, depending on size and fracture. I do not know how long
this earthquake swarm is going to last, but I do not belive it is over
when I write this at 19:13 UTC.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Wave Id's
From: John or Jan Lahr JohnJan@........
Date: Thu, 11 Jan 2007 11:22:54 -0800
Ted,
There is a free PC program that is great for understanding many of
the phases on a seismogram.
I always find the web site via google: alan jones seismic
Alan's site will be the first hit.
Download the program SeismicWaves from his site. This program shows
how the wave fronts
progress through the Earth, bouncing, converting, and refracting at
the major layers. At the same
time, actual seismograms are displayed as they would have looked when
being recorded. The
phases are labeled on the seismograms as they arrive. The
earthquakes are generally played
in speeded up time, as otherwise it would take 20 minutes to see the
first waves reach all the
way through the Earth.
For a full list of phases and ray-path diagrams, check out this site:
http://www.isc.ac.uk/Documents/IASPEI/sspl.html
Note that in some of the diagrams, where the paths for P and S are the same,
paths are labeled P/S, which means P or S. Similarly, Pdiff and Sdiff paths
are shown with the same red line.
Cheers,
John
At 10:08 AM 1/11/2007, you wrote:
>Hi All, It was pointed out that within Winquake software is a
>pulldown menu which places the various wave id markers. Is there a
>page avail which explains what the id's initials stand for? As an
>example P= primary S= secondary SSS,? LQ, LR and so on.
>
>Thanks, Ted
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Vertical sensor
From: "tchannel" tchannel@..............
Date: Thu, 11 Jan 2007 17:09:47 -0700
Hi Folks, In the last week or two, I have been testing my Vertical =
sensor, I have received several events.
I have a question about two: I don't remember the details of each =
event. =20
One event was due East about 400 miles, the other was due South about =
400 miles, they were both about 3.5M
The vertical recorded the one from the South just fine, but recorded =
nothing on the one from the East.
The vertical sensor is pointing N/S. If this was a Horz sensor I =
would expect this, but is a Vertical also, sensitive to the direction?
The hinge I made does keep the arm from moving left/right similar to the =
AS1.
Thanks, Ted
Hi Folks, In the last week or =
two, I have=20
been testing my Vertical sensor, I have received several =
events.
I have a question about two: I =
don't remember=20
the details of each event.
One event was due East about 400 miles, =
the other=20
was due South about 400 miles, they were both about 3.5M
The vertical recorded the one from the =
South just=20
fine, but recorded nothing on the one from the East.
The vertical sensor is pointing=20
N/S. If this was a Horz sensor I would expect this,=20
but is a Vertical also, sensitive to the direction?
The hinge I made does keep the arm from =
moving=20
left/right similar to the AS1.
Thanks, Ted
Subject: Kuril island 8.2Mw earthquake
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 13 Jan 2007 09:31:33 +0000
Hi all
I did record the 8.2Mw Kuril Island earthquake, it appears so good that
it is even visable on my online helcorder (plots). But that is really
unusual for a earthquake that is nearly 7200 km away from me.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Kuril island 8.2Mw earthquake <<< EUREKA>>>>>>
From: jimo17@........
Date: Sat, 13 Jan 2007 18:14:26 -0800
Hi Jon-
Eureka<<< Your geophones are working well.....M8.2 at ~8,000 kms
Always impressive to see an inexpensive jug doing amazing things..
Some Comments to improve your Recordings:
Before filtering observe the Power Spectra and decide what is signal and
noise peaks.
1. Look at Spectra- notice peak around 0.01-0.1
2. Use BP filter with 2 poles filter around 0.01-0.1, or some where in
that vicinity.
Remember the tighter the BP the more ringing you create in the
filtered record- I like a decade but you can use less.
Results will show the S arrivals and Surface waves much clearer.
Use option to mark these arrivals for you.
4. On the Teleseismic events consider resampling from 100 Hz (100 SPS) to
25 Hz to reduce the # of samples by 1/4.
5. You can also put in the Equalizer (electronic) circuit to change the
4.5 Hz to ~0.4Hz, which makes a big difference.
Keep up the good work as you are really doing well.
I can remember well when I recorded my first Teleseismic event with the
L15b-4.5Hz jug<<<<< Jim
Jim O'Donnell
Geological/Geophysical Consultant
GEOTECHNICAL APPLICATIONS
Las Vegas, Nevada
geophysics@..........
On Sat, 13 Jan 2007 09:31:33 +0000 =?ISO-8859-1?Q?J=F3n_Fr=EDmann?=
writes:
> Hi all
>
> I did record the 8.2Mw Kuril Island earthquake, it appears so good
> that
> it is even visable on my online helcorder (plots). But that is
> really
> unusual for a earthquake that is nearly 7200 km away from me.
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Kuril island 8.2Mw earthquake <<< EUREKA>>>>>>
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Mon, 15 Jan 2007 14:00:22 +0000
Hi
I will soon add long period channels to my hardware and a long period
sensor too. So I don't have any reason to extend the geophone down to
that level.
The frequancy of the Kuril island 8.2Mw earthquake was hig enugh so that
I was able to see on frequancyes above 4Hz, even well above 10Hz. That
is unusual. I did lowpass it down to 4Hz for cleanup on the signal.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Kuril island 8.2Mw earthquake
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 16 Jan 2007 13:16:31 +0000
Hi all
emsc-csem has intresting info on the Kuril island earthquakes, both of
the large earthquake that have struck here with less then 60 days
between them.
Here is the url,
http://www.emsc-csem.org/index.php?page=current&sub=recent&evt=20061115_KURILS
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Earthquake lockin in Iceland
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 16 Jan 2007 19:17:40 +0000
Hi all
Iceland appears to be going trugh a rather strange event. This week,
that is Monday to today (16.01.2007) there have only been like 10
earthquakes in whole Iceland. Usaual by this time of the week, IMO has
recored learny 50 - 100 earthquakes, in a normal week. I call this
earthquake lockin, that means that something in the earth crust is stuck
and prevents earthquakes. What it is anybody guess. This was ongoing all
of 2006 and it is still going on. I don't think this good sign at all.
Whatever happen, there is a good chance it happens soon and is going to
be a large type of event, but what type of event I have no idea. There
is a chance a volcano is (in my opinion) that createing this tensions in
the crust.
This is just my speculation.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Noobie Greetings
From: "Michael Kimzey, D.O." mckimzey@...........
Date: Tue, 16 Jan 2007 20:51:31 -0500
Hi all.
I'm new to the group and just wanted to get my feet wet with a post,
observations and some questions. After many years of indecision, I finally
made the plunge and built a Lehman. It is currently operating in a crawl
space under the family room. I thought that it would be somewhat quiet
there, but it seems that some poured concrete over dirt isn't that quiet.
Additionally, I am 50 feet from a fairly busy road...but I'll take what I
can get.
With the help of Larry (very helpful and patient with questions), I got
the electronics up and running and the rest of the story with pictures can
be viewed at http://www.mckimzey.com/seismology.html I haven't seen any
activity yet, but did get a teaser with the recent Alaska quake...would have
recorded it but that was the 12 hours that the system was down for some
early modifications....hummf.
Right now I'm oil damped, but hope to make the metal damper. I have seen
that both copper and aluminum are used. Is either better than the other? I
don't have ready access to copper plate (is it available at Home Depot or
Lowes?) so I was going to use a pipe that I flattened. What kind of
thickness is needed?
I'm running WinSDR and I fiddled around with the gain on the board. Is
there a baseline count that I should aim for...I think that someone put it
at around 100 or 200 (boy, that 4th quarter list archive was looong). Also,
does it matter if I display raw or filtered data? I'm using the default
WinSDR settings for alarms and filters.
Finally, now that I've got the bug, of course I want more instruments. I
was thinking about the SG sensor, but the volksmeter has my interest piqued.
I heard that it might only be ready-made, but maybe it wouldn't be too
difficult to build one. The upright(s) of aluminum; shaft of aluminum
(although the PDF looks like it was made of brass). The plates could be
made of PCB board, etched if needed. It would just be the electronics that
I would need to buy. One of the things that I find neat about that design
is that it probably could be minimized to a size where it could fit in a 6
inch tube and be sunk several feet/meters in the ground (with remote motor
leveling and such)
Ok, enough of my ideas. My ignorance of seismology betrays me. Any
thoughts or ideas would be welcome. Thanks!
- Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: Larry Cochrane lcochrane@..............
Date: Wed, 17 Jan 2007 02:11:30 -0800
Hi Mike,
Welcome to the group. When setting the gain you should use the raw data from the A/D
converter, so you should use the unfiltered data.
Regards,
Larry Cochrane
Redwood City, PSN
Michael Kimzey, D.O. wrote:
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I finally
> made the plunge and built a Lehman. It is currently operating in a crawl
> space under the family room. I thought that it would be somewhat quiet
> there, but it seems that some poured concrete over dirt isn't that quiet.
> Additionally, I am 50 feet from a fairly busy road...but I'll take what I
> can get.
> With the help of Larry (very helpful and patient with questions), I got
> the electronics up and running and the rest of the story with pictures can
> be viewed at http://www.mckimzey.com/seismology.html I haven't seen any
> activity yet, but did get a teaser with the recent Alaska quake...would have
> recorded it but that was the 12 hours that the system was down for some
> early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other? I
> don't have ready access to copper plate (is it available at Home Depot or
> Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong). Also,
> does it matter if I display raw or filtered data? I'm using the default
> WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest piqued.
> I heard that it might only be ready-made, but maybe it wouldn't be too
> difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics that
> I would need to buy. One of the things that I find neat about that design
> is that it probably could be minimized to a size where it could fit in a 6
> inch tube and be sunk several feet/meters in the ground (with remote motor
> leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "Dewayne" n0ssy@...........
Date: Wed, 17 Jan 2007 08:48:25 -0700
Welcome to the group Michael.
If you want to build a vertical seismometer, look at my design @
http://www.jclahr.com/science/psn/hill/.
I constructed this one about two years ago and it has preformed very well.
My seismometer is also located in my crawl space. I poured a small 4'x4'x6"
concrete pad to set my seismometers on. I used straight
mortar (lots of dust) as it doesn't contain any rocks. I used mortar to
prevent any thermo-dynamic differences between the mortar and rocks
that are in concrete.
I am using an oil dampimg system. I have tried cooking oil, transmisson
fluid and motor oil. All of these are not heavy enough to give a good
damping. My next try is going to be STP oil treatment. If STP don't work
I'll have to redo the tub to something with a larger surface area.
Anyway good luck and have fun.
Dewayne
----- Original Message -----
From: "Michael Kimzey, D.O."
To:
Sent: Tuesday, January 16, 2007 6:51 PM
Subject: Noobie Greetings
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I
> finally made the plunge and built a Lehman. It is currently operating in
> a crawl space under the family room. I thought that it would be somewhat
> quiet there, but it seems that some poured concrete over dirt isn't that
> quiet. Additionally, I am 50 feet from a fairly busy road...but I'll take
> what I can get.
> With the help of Larry (very helpful and patient with questions), I
> got the electronics up and running and the rest of the story with pictures
> can be viewed at http://www.mckimzey.com/seismology.html I haven't
> seen any activity yet, but did get a teaser with the recent Alaska
> quake...would have recorded it but that was the 12 hours that the system
> was down for some early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other?
> I don't have ready access to copper plate (is it available at Home Depot
> or Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong).
> Also, does it matter if I display raw or filtered data? I'm using the
> default WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest
> piqued. I heard that it might only be ready-made, but maybe it wouldn't be
> too difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics
> that I would need to buy. One of the things that I find neat about that
> design is that it probably could be minimized to a size where it could fit
> in a 6 inch tube and be sunk several feet/meters in the ground (with
> remote motor leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with the body of the
> message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "Dewayne" n0ssy@...........
Date: Wed, 17 Jan 2007 08:48:25 -0700
Welcome to the group Michael.
If you want to build a vertical seismometer, look at my design @
http://www.jclahr.com/science/psn/hill/.
I constructed this one about two years ago and it has preformed very well.
My seismometer is also located in my crawl space. I poured a small 4'x4'x6"
concrete pad to set my seismometers on. I used straight
mortar (lots of dust) as it doesn't contain any rocks. I used mortar to
prevent any thermo-dynamic differences between the mortar and rocks
that are in concrete.
I am using an oil dampimg system. I have tried cooking oil, transmisson
fluid and motor oil. All of these are not heavy enough to give a good
damping. My next try is going to be STP oil treatment. If STP don't work
I'll have to redo the tub to something with a larger surface area.
Anyway good luck and have fun.
Dewayne
----- Original Message -----
From: "Michael Kimzey, D.O."
To:
Sent: Tuesday, January 16, 2007 6:51 PM
Subject: Noobie Greetings
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I
> finally made the plunge and built a Lehman. It is currently operating in
> a crawl space under the family room. I thought that it would be somewhat
> quiet there, but it seems that some poured concrete over dirt isn't that
> quiet. Additionally, I am 50 feet from a fairly busy road...but I'll take
> what I can get.
> With the help of Larry (very helpful and patient with questions), I
> got the electronics up and running and the rest of the story with pictures
> can be viewed at http://www.mckimzey.com/seismology.html I haven't
> seen any activity yet, but did get a teaser with the recent Alaska
> quake...would have recorded it but that was the 12 hours that the system
> was down for some early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other?
> I don't have ready access to copper plate (is it available at Home Depot
> or Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong).
> Also, does it matter if I display raw or filtered data? I'm using the
> default WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest
> piqued. I heard that it might only be ready-made, but maybe it wouldn't be
> too difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics
> that I would need to buy. One of the things that I find neat about that
> design is that it probably could be minimized to a size where it could fit
> in a 6 inch tube and be sunk several feet/meters in the ground (with
> remote motor leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with the body of the
> message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "tchannel" tchannel@..............
Date: Wed, 17 Jan 2007 09:09:15 -0700
Hi Mike, Congratulations on a nice design, I build two Lehman's and a
Vertical, email me if you would like to see pictures as I have no way to
post them. Your Lehman should work great. My Lehman is in the basements
and I pick up Earthquakes fine, but also pick up road construction, digging
in the earth. I do not pick up any traffic, not even trucks, just weather,
cold fronts, and the city daytime noises.
I also used a ball bearing on my arm, but retained it between two drill bit
shanks. The ball ride in between the two cylinders so it does not move up
or down out of the small "V" formed by the shanks. Let us know when you
record your first event and maybe you will post them on .PSN
EVENTS. Ted
----- Original Message -----
From: "Michael Kimzey, D.O."
To:
Sent: Tuesday, January 16, 2007 6:51 PM
Subject: Noobie Greetings
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I
> finally made the plunge and built a Lehman. It is currently operating in
> a crawl space under the family room. I thought that it would be somewhat
> quiet there, but it seems that some poured concrete over dirt isn't that
> quiet. Additionally, I am 50 feet from a fairly busy road...but I'll take
> what I can get.
> With the help of Larry (very helpful and patient with questions), I
> got the electronics up and running and the rest of the story with pictures
> can be viewed at http://www.mckimzey.com/seismology.html I haven't
> seen any activity yet, but did get a teaser with the recent Alaska
> quake...would have recorded it but that was the 12 hours that the system
> was down for some early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other?
> I don't have ready access to copper plate (is it available at Home Depot
> or Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong).
> Also, does it matter if I display raw or filtered data? I'm using the
> default WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest
> piqued. I heard that it might only be ready-made, but maybe it wouldn't be
> too difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics
> that I would need to buy. One of the things that I find neat about that
> design is that it probably could be minimized to a size where it could fit
> in a 6 inch tube and be sunk several feet/meters in the ground (with
> remote motor leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with the body of the
> message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Wed, 17 Jan 2007 17:51:59 +0000
Hi Michael
Welcome to this hobby. This is quite intresting hobby, when there is
something going on. But we also see some dead time too, when there is
nothing going on. I have one 4.5Hz sensor connected at the moment. But I
have plans to have more sensor up and running soon. I also have plans to
add three long period sensors to my system.
Check out my webpage, but you can see there my plots and other plots
also.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "tchannel" tchannel@..............
Date: Wed, 17 Jan 2007 17:41:02 -0700
Hi Mike, As to your damper, I too started with fluids, The magnetic
damper, that Chris told me about works like a champ. He has this design
posted. In your cast , you have lots of room, so you could hang an Alum or
Copper plate from your arm and have it pass between the magnet
sandwich/assm. sliding it in or out as needed. It allows you to move the
magnetic closer for a stronger effect. I use a piece of Alum about
1/16-1/8"? thick. It was a Alum lid for a plastic elect. project box,
Radioshack, the box came with a plastic lid and and Alum lid.
Ted
----- Original Message -----
From: "Michael Kimzey, D.O."
To:
Sent: Tuesday, January 16, 2007 6:51 PM
Subject: Noobie Greetings
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I
> finally made the plunge and built a Lehman. It is currently operating in
> a crawl space under the family room. I thought that it would be somewhat
> quiet there, but it seems that some poured concrete over dirt isn't that
> quiet. Additionally, I am 50 feet from a fairly busy road...but I'll take
> what I can get.
> With the help of Larry (very helpful and patient with questions), I
> got the electronics up and running and the rest of the story with pictures
> can be viewed at http://www.mckimzey.com/seismology.html I haven't
> seen any activity yet, but did get a teaser with the recent Alaska
> quake...would have recorded it but that was the 12 hours that the system
> was down for some early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other?
> I don't have ready access to copper plate (is it available at Home Depot
> or Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong).
> Also, does it matter if I display raw or filtered data? I'm using the
> default WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest
> piqued. I heard that it might only be ready-made, but maybe it wouldn't be
> too difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics
> that I would need to buy. One of the things that I find neat about that
> design is that it probably could be minimized to a size where it could fit
> in a 6 inch tube and be sunk several feet/meters in the ground (with
> remote motor leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with the body of the
> message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Pendulum Q
From: Larry Cochrane lcochrane@..............
Date: Thu, 18 Jan 2007 21:48:09 -0800
Hi everyone,
Dr. Randall Peters has ask me to forward the following to the list.
-Larry
I have noticed that many of you have great interest in detecting small teleseismic
earthquakes, but probably don't have a great deal of interest in carefully studying
the temporal features of what gets recorded. Thus I have a recommendation for those
of you who are using long-period instruments, such as the Lehman or a folded
pendulum. If your instrument's natural period is in the vicinity of about 20 s, then
try the following simple experiment--remove all external damping from your
instrument. In other words, take off the magnets, or remove the oil pot. I have
already learned to wear the label comfortably, but before you view me as a heretic
(which some will do, since anything other than near-critical damping is viewed as
ridiculous) consider the following.
Your undamped pendulum's acceleration responsively at 20 s will be increased by the
value of Q. My guess is that many of you will thus see at least a 10- to 50-fold
increase in your ability to then detect small, distant earthquakes. No doubt the
objection to be raised by some to my recommendation will be--BUT the transient
response of the pendulum will 'mess up' everything! Yes, you will have immeasurably
complicated things if your interest is traditional. This traditional viewpoint is
one that I believe will become for some observers increasingly antiquated and
irrelevant. In the days before computers, such a mode of operation was indeed
ridiculous for those who wanted to see all the intricacies of arrival time features
governed by phase, etc. But now with the computer we have the ability to graph what
is probably the single-most-important feature (to one with a single instrument as
opposed to an array of them) of what the seismometer is telling us about the earth's
motion--the POWER. By using the computer to compensate for the transfer function of
the pendulum, one can generate a reasonably good power spectral density no matter
whether the instrument is damped or undamped. I will provide details on this
important calculation for those who are interested.
What is the biggest problem with the traditional approach which I'm suggesting
that some of you abandon?. Consider an analogy from the electromagnetic case. How
does everybody detect radio (TV or countless other types of similar) waves? The
answer--by 'TUNING' their receiver with a relatively high Q. Of course, if you want
to see a whole lot of different regions of the E-M spectrum you must be able to
adjust the bandpass of your receiver. In the case of the earth, a whole lot of
different natural period pendulums would be necessary to see everything of interest.
Think about the following: If communication systems were to operate in the manner
of seismology, we would just pick up everything in the electromagnetic spectrum with
a broadband antenna and try to sort things out with sophisticated electronics!
I have already demonstrated the viability of this method in the case of
microseisms with periods around 4 s; c.f. the paper "Compound Pendulum to Monitor
Hurricanes and Tropical Storms"
http://physics.mercer.edu/hpage/compound/compound.html There's no
reason the same thing can't be done for the longer period region of teleseismic
earthquakes (around 20 s). I predict you will be AMAZED at what starts to show up in
your records.
I hope that some of you will try this surprisingly simple experiment and tell me of
your excitement after a few days watching the output from your seismograph.
Randall Peters
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: spring for AS1 type seismometer
From: "Thomas Dick" dickthomas01@.............
Date: Fri, 19 Jan 2007 16:36:01 -0600
Where do you suggest I look for a spring for this type of seismometer -- =
I understand the spring tends to be temperature sensitive?
Where do you suggest I look for a =
spring for this=20
type of seismometer -- I understand the spring tends to be =
temperature=20
sensitive?
Subject: Re: spring for AS1 type seismometer
From: "Dewayne" n0ssy@...........
Date: Fri, 19 Jan 2007 16:08:59 -0700
Hopefully you have a Lowes hardware close by. If so go to their =
nut/bolts/screw area. They should also have springs in this area. Look =
for a spring with
the part number of "C 311". It's 1/2" dia and about 11" (?) long. You =
will have to cut the spring to size after you have everything assembled. =
I have not heard about any
temperature sensitive problems and I don't have any, but this maybe =
because it is enclosed in a heat stabilized enclosure.
Dewayne
----- Original Message -----=20
From: Thomas Dick=20
To: psn-l@.................
Sent: Friday, January 19, 2007 3:36 PM
Subject: spring for AS1 type seismometer
Where do you suggest I look for a spring for this type of seismometer =
-- I understand the spring tends to be temperature sensitive?
Hopefully you have a Lowes hardware =
close by. If so=20
go to their nut/bolts/screw area. They should also have springs in this =
area.=20
Look for a spring with
the part number of "C 311". It's 1/2" =
dia and about=20
11" (?) long. You will have to cut the spring to size after you have =
everything=20
assembled. I have not heard about any
temperature sensitive problems and I =
don't have=20
any, but this maybe because it is enclosed in a heat stabilized=20
enclosure.
Where do you suggest I look for a =
spring for this=20
type of seismometer -- I understand the spring tends to be =
temperature=20
sensitive?
Subject: Re: spring for AS1 type seismometer
From: "tchannel" tchannel@..............
Date: Fri, 19 Jan 2007 16:10:19 -0700
Hi Thomas, I recently finished a nice little vertical spring sensor, =
it is working well for me. For pictures and info just email me, =
tchannel@.............. The spring, I used, is a zero-length spring =
from Ace Hardware, 6" in length "Servalite #59"
----- Original Message -----=20
From: Thomas Dick=20
To: psn-l@.................
Sent: Friday, January 19, 2007 3:36 PM
Subject: spring for AS1 type seismometer
Where do you suggest I look for a spring for this type of seismometer =
-- I understand the spring tends to be temperature sensitive?
Hi=20
Thomas, I recently finished a nice little vertical spring =
sensor, it=20
is working well for me. For pictures and info just email me, tchannel@.............. =
=20
The spring, I used, is a zero-length spring from Ace Hardware, 6=94 =
in length=20
=93Servalite #59=94
Where do you suggest I look for a =
spring for this=20
type of seismometer -- I understand the spring tends to be =
temperature=20
sensitive?
Subject: Re: spring for AS1 type seismometer
From: ChrisAtUpw@.......
Date: Fri, 19 Jan 2007 20:34:00 EST
In a message dated 19/01/2007, n0ssy@........... writes:
Hopefully you have a Lowes hardware close by. Look for a spring with
the part number of "C 311". It's 1/2" dia and about 11" (?) long. You will
have to cut the spring to size after you have everything assembled. I have not
heard about any
temperature sensitive problems and I don't have any, but this maybe because
it is enclosed in a heat stabilized enclosure.
Hi Tom,
Steel springs are quite temperature sensitive, but this is not a problem
if you are only looking for a 1.5 sec period, like on an AS-1. It gets to be
a problem if you try to extend the period beyond about 5 seconds. Using
about this period makes designing a long period compensating amplifier much
easier. See _http://jclahr.com/science/psn/roberts/index.html_
(http://jclahr.com/science/psn/roberts/index.html)
Regards,
Chris
In a message dated 19/01/2007, n0ssy@........... writes:
Hopefully you have a Lowes hardware close=
by.=20
Look for a spring with
the part number of "C 311". It's 1/2" dia=
and=20
about 11" (?) long. You will have to cut the spring to size after you have=
=20
everything assembled. I have not heard about any
temperature sensitive problems and I don'=
t have=20
any, but this maybe because it is enclosed in a heat stabilized=20
enclosure.
Hi Tom,
Steel springs are quite temperature sensitive,=20=
but=20
this is not a problem if you are only looking for a 1.5 sec period, like on=20=
an=20
AS-1. It gets to be a problem if you try to extend the period beyond about 5=
=20
seconds. Using about this period makes designing a long period compensating=20
amplifier much easier. See http://jclahr.com/=
science/psn/roberts/index.html
Regards,
Chris
Subject: Re:Pendulum Q
From: Bobhelenmcclure@.......
Date: Fri, 19 Jan 2007 22:05:52 EST
Hi all,
What Dr. Peters wants us to try left me stunned. All that will result is a
narrow-band modulated 20 Hz carrier without any useful event information.
Bob
Hi all,
What Dr. Peters wants us to try left me stunned. All that will result i=
s a=20
narrow-band modulated 20 Hz carrier without any useful event information.
Bob
Subject: Re: Pendulum Q
From: ian ian@...........
Date: Sat, 20 Jan 2007 10:51:39 +0000
I had a brief look at it and couldn't find the referred mathematical
processing needed to extract the information on a now "super sensitised"
detector. I can only guess that this would be based on the natural
decay of the signal if it received a momentary stimulus compared to what
was actually going on.
Ian
Bobhelenmcclure@....... wrote:
> Hi all,
>
> What Dr. Peters wants us to try left me stunned. All that will result
> is a narrow-band modulated 20 Hz carrier without any useful event
> information.
>
> Bob
--
I had a brief look at it and couldn't find the referred mathematical
processing needed to extract the information on a now "super
sensitised" detector. I can only guess that this would be based on the
natural decay of the signal if it received a momentary stimulus
compared to what was actually going on.
What Dr. Peters wants us to try left me stunned. All that will
result is a narrow-band modulated 20 Hz carrier without any useful
event information.
Bob
--
Subject: Public Seismic Network - Dominica Forum
From: "Wayne Abraham" gold1146@...........
Date: Sat, 20 Jan 2007 13:27:27 +0000
Hello All
I have just setup a discussion board for the Public Seismic Network on
Dominica. Although the forums I have setup are only for discussions on
Dominica, I am willing to expand it to facilitate all of you in the PSN
community. You can visit the board at http://dominicapsn.editboard.com. If
you wish to participate in any of the forums or would like me to start new
forums to cater for your interest, just register and send me (admin) a
private message from the board. If you would like to moderate your own forum
I can also accommodate you.
Wayne
Public Seismic Network - Dominica
_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today it's FREE!
http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Pendulum Q
From: Bobhelenmcclure@.......
Date: Sat, 20 Jan 2007 09:51:44 EST
Correction: 0.05Hz, not 20Hz. With an information bandwidth of around
0.0025Hz.
Bob
Correction: 0.05Hz, not 20Hz. With an information bandwidth of aro=
und=20
0.0025Hz.
Bob
Subject: questions on spring loaded vertical pendulum
From: "Thomas Dick" dickthomas01@.............
Date: Sat, 20 Jan 2007 09:29:26 -0600
1. If you remove the magnet from the boom -- what is the anticipated =
mass to put on the end of the boom -- or is it dependent on the spring's =
tension.
2. is the period of the instrument affected by the length of the boom, =
size of the base plate, length of the spring or mass
1. If you remove the magnet from the =
boom -- what=20
is the anticipated mass to put on the end of the boom -- or is it =
dependent on=20
the spring's tension.
2. is the period of the instrument =
affected by the=20
length of the boom, size of the base plate, length of the spring =
or=20
mass
Subject: Re: questions on spring loaded vertical pendulum
From: "tchannel" tchannel@..............
Date: Sat, 20 Jan 2007 09:26:46 -0700
Hi Thomas, There is a handy "Spring Calculator.exe" which I found =
helpful. Someone will point it out to you? I don't have the site.
I found the period to be effected by the amount of pull on the spring, =
that could be "whatever" expands the spring, arm-connection point, =
vertical connection point, mass, angle, etc. Doing a simple test, to =
measure if my spring was zero length-type, I hung it from a string and =
added weight, which add explanation, which added period. Ted
----- Original Message -----=20
From: Thomas Dick=20
To: psn-l@.................
Sent: Saturday, January 20, 2007 8:29 AM
Subject: questions on spring loaded vertical pendulum
1. If you remove the magnet from the boom -- what is the anticipated =
mass to put on the end of the boom -- or is it dependent on the spring's =
tension.
2. is the period of the instrument affected by the length of the boom, =
size of the base plate, length of the spring or mass
Hi Thomas, There is a handy "Spring =
Calculator.exe"=20
which I found helpful. Someone will point it out to you? I don't =
have the=20
site.
I found the period to be effected by =
the amount of=20
pull on the spring, that could be "whatever" expands the spring, =
arm-connection=20
point, vertical connection point, mass, angle, etc. Doing a simple =
test,=20
to measure if my spring was zero length-type, I hung it from a string =
and added=20
weight, which add explanation, which added period. =
Ted
Subject: questions on spring =
loaded=20
vertical pendulum
1. If you remove the magnet from the =
boom -- what=20
is the anticipated mass to put on the end of the boom -- or is it =
dependent on=20
the spring's tension.
2. is the period of the instrument =
affected by=20
the length of the boom, size of the base plate, length of the =
spring or=20
mass
Subject: Re: Pendulum Q
From: ChrisAtUpw@.......
Date: Sat, 20 Jan 2007 20:45:03 EST
In a message dated 20/01/2007, Bobhelenmcclure@....... writes:
Hi all,
What Dr. Peters wants us to try left me stunned. All that will result is a
narrow-band modulated 20 Hz carrier without any useful event information.
Bob
Hi Bob,
You mean 20 sec period ~ 0.05 Hz?
It is usually a good idea to scan through the references given in
letters before commenting.
In this case see _http://physics.mercer.edu/hpage/compound/compound.html_
(http://physics.mercer.edu/hpage/compound/compound.html)
Professor Peters uses a capacitative position detector with a DC output.
This is sensitive to a much wider range of signals than inductive magnetic
detectors and can measure long period tilt signals. He used a tuned detector
to monitor storm background microseism signals.
The current suggestion however, is to use your Lehman effectively
'tuned' at about 20 sec period to dig out small long period seismic signals from
the noisy background. Many of the regional Love and Rayleigh waves are about
this period - this is around the standard observing window for measuring quake
magnitudes with surface waves.
If you then process the signal for power you should get the envelope of
the quake signal. Why you say that this is not useful event information?
I had a brief look at it and couldn't find the referred mathematical
processing needed to extract the information on a now "super sensitised" detector.
I can only guess that this would be based on the natural decay of the signal
if it received a momentary stimulus compared to what was actually going on.
Ian
If you read the text carefully, you will see Professor Peters' offer:-
In the days before computers, undamped operation was indeed ridiculous
for those who wanted to see all the intricacies of arrival time features
governed by phase, etc. But with a computer we now have the ability to graph what
is probably the single-most-important feature (to one with a single
instrument as opposed to an array of them) of what the seismometer is telling us
about the earth's motion - the POWER. By using the computer to compensate for
the transfer function of the pendulum, one can generate a reasonably good power
spectral density no matter whether the instrument is damped or undamped. I
will provide details on this important calculation for those who are
interested.
Regards,
Chris Chapman
In a message dated 20/01/2007, Bobhelenmcclure@....... writes:
What Dr. Peters wants us to try left me stunned. All that will result=
is=20
a narrow-band modulated 20 Hz carrier without any useful event=20
information.
Bob
Hi Bob,
You mean 20 sec period ~ 0.05 Hz?
It is usually a good idea to scan through the=20
references given in letters before commenting.
In this case see http://physi=
cs.mercer.edu/hpage/compound/compound.html
Professor Peters uses a capacitative position=20
detector with a DC output. This is sensitive to a much wider range of=20
signals than inductive magnetic detectors and can measure long period tilt=20
signals. He used a tuned detector to monitor storm background microseis=
m=20
signals.
The current suggestion however, is to use your=20
Lehman effectively 'tuned' at about 20 sec period to dig out small long peri=
od=20
seismic signals from the noisy background. Many of the regional Love and=20
Rayleigh waves are about this period - this is around the standard observing=
=20
window for measuring quake magnitudes with surface waves.
If you then process the signal for power you sh=
ould=20
get the envelope of the quake signal. Why you say that this is not useful ev=
ent=20
information?
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>I had a=20
brief look at it and couldn't find the referred mathematical processing ne=
eded=20
to extract the information on a now "super sensitised" detector. I c=
an=20
only guess that this would be based on the natural decay of the signal if=20=
it=20
received a momentary stimulus compared to what was actually going=20
on. Ian
If you read the text carefully, you will see=20
Professor Peters' offer:-
In the days before computers, undamped operatio=
n=20
was indeed ridiculous for those who wanted to see all the intricacies of arr=
ival=20
time features governed by phase, etc. But with a computer we=20
now have the ability to graph what is probably the single-most-importan=
t=20
feature (to one with a single instrument as opposed to an array of them) of=20=
what=20
the seismometer is telling us about the earth's motion - the POWER. By=
=20
using the computer to compensate for the transfer function of the pendulum,=20=
one=20
can generate a reasonably good power spectral density no matter whether the=20
instrument is damped or undamped. I will provide details on this=20
important calculation for those who are interested.
Regards,
Chris Chapman
Subject: Re: questions on spring loaded vertical pendulum
From: Bobhelenmcclure@.......
Date: Sat, 20 Jan 2007 21:59:11 EST
Please look at:
_http://www.seismicnet.com/psnlist/061130_182932_1.html_
(http://www.seismicnet.com/psnlist/061130_182932_1.html)
for information about SpringCalc.exe, a design tool I developed for vertical
seismometers. There are also some relevant links in the letter.
Bob
for information about SpringCalc.exe, a design tool I developed for=20
vertical seismometers. There are also some relevant links in the letter.
Bob
Subject: Re: Pendulum Q
From: "Geoffrey" gmvoeth@...........
Date: Sat, 20 Jan 2007 21:23:17 -0700
You can make three or more narrow band high Q band
pass filters and sum them all together using
various gains of your own free choice.
----- Original Message -----
From:
To:
Sent: Saturday, January 20, 2007 7:51 AM
Subject: Re: Pendulum Q
> Correction: 0.05Hz, not 20Hz. With an information bandwidth of around
> 0.0025Hz.
>
> Bob
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Pendulum Q
From: Larry Cochrane lcochrane@..............
Date: Sat, 20 Jan 2007 22:52:23 -0800
From Randall. -Larry
Notice, Bob, what I said about the matter. If the 'purity' of the events is not
what you are most interested in, then give it a try. The 'carrier' (a misnomer)
you mention is not 20 Hz but 50 mHz (much lower frequency than body wave
values). There is useful information concerning the energy of the earthquake by
doing the power spectral density (corrected for the transfer function of the
instrument; i.e., the transient, or 'ringing' features)-- independent of the
'events'. My guess is that most people don't really use the details of the event
information quantitatively anyway. You go find out where the earthquake occurred
by consulting USGS webpages after you've seen it on your seismograph. It is not
the time difference between P and S events that serves as the primary means for
locating an earthquake by USGS anyway. The errors of a calculation based on the
difference in speeds of the longitudinal and transverse components are much worse
than a calculation using only the P event from two or more instruments
geographically separated in azimuth by a large amount relative to the
earthquake. In other words, USGS uses triangulation as the means for localizing
earthquakes. Yes it is nice to observe the S wave delay relative to the P wave
as a rough measure of how far away the earthquake was. I figured, however, that
some of you would like to just 'see' the surface waves from weaker, distant
earthquakes. I predict that by the means I mentioned you will see some of them
that otherwise would go unnoticed. Before anybody makes sweeping generalizations
about my heresy, I suggest that you first take a look at the graphs that I have
posted on my webpage at http://physics.mercer.edu/hpage/listserve.gif It shows
that the undamped pendulum (in spite of ringing, following arrival of each of the
P and S waves for the case shown-- nevertheless contains decent information
concerning the spectral features of the most important piece of the record; i.e.,
the surface waves, whose frequencies are distributed between approximately 7 s
and 70 s. The very longest periods differ between the VolksMeter record and the
undamped pendulum record (PSD's), but this might be due in part to the different
locations of the instruments. The undamped instrument was on a home-built 'pier'
in my home basement, whereas the VolksMeter was on the concrete-slab floor of the
Willett Science Center here at Mercer University (about two miles from my
house). The building may be hindered with respect to the tilts occurring at the
longest periods. For you 'purists', note the fact that the first-disturbance
arrival times of both P and S are abundantly clear, including the delta time
between them--closely correlated with the 'proper' instrument, our VolksMeter. I
expect similar results with an undamped, tuned garden-gate pendulum with a period
5 times longer at 20 s--the big difference being that the surface waves that
characterize the teleseismic earthquake record will be enhanced significantly
because their frequencies are close to the high-Q resonance of the instrument.
Randall
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: Pendulum Q
From: "Stephen Hammond" shammon1@.............
Date: Sun, 21 Jan 2007 00:40:20 -0800
Boy, this is getting a little mixed up. Are we talking about the
response of the instrument or the site response of the recording
location?
Regards, Steve Hammond PSN San Jose, Aptos Ca.
-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@...............
On Behalf Of Larry Cochrane
Sent: Saturday, January 20, 2007 10:52 PM
To: psn-l@..............
Subject: Re: Pendulum Q
From Randall. -Larry
Notice, Bob, what I said about the matter. If the 'purity' of the
events is not
what you are most interested in, then give it a try. The 'carrier' (a
misnomer)
you mention is not 20 Hz but 50 mHz (much lower frequency than body wave
values). There is useful information concerning the energy of the
earthquake by
doing the power spectral density (corrected for the transfer function of
the
instrument; i.e., the transient, or 'ringing' features)-- independent of
the
'events'. My guess is that most people don't really use the details of
the event
information quantitatively anyway. You go find out where the earthquake
occurred
by consulting USGS webpages after you've seen it on your seismograph.
It is not
the time difference between P and S events that serves as the primary
means for
locating an earthquake by USGS anyway. The errors of a calculation
based on the
difference in speeds of the longitudinal and transverse components are
much worse
than a calculation using only the P event from two or more instruments
geographically separated in azimuth by a large amount relative to the
earthquake. In other words, USGS uses triangulation as the means for
localizing
earthquakes. Yes it is nice to observe the S wave delay relative to the
P wave
as a rough measure of how far away the earthquake was. I figured,
however, that
some of you would like to just 'see' the surface waves from weaker,
distant
earthquakes. I predict that by the means I mentioned you will see some
of them
that otherwise would go unnoticed. Before anybody makes sweeping
generalizations
about my heresy, I suggest that you first take a look at the graphs that
I have
posted on my webpage at http://physics.mercer.edu/hpage/listserve.gif
It shows
that the undamped pendulum (in spite of ringing, following arrival of
each of the
P and S waves for the case shown-- nevertheless contains decent
information
concerning the spectral features of the most important piece of the
record; i.e.,
the surface waves, whose frequencies are distributed between
approximately 7 s
and 70 s. The very longest periods differ between the VolksMeter record
and the
undamped pendulum record (PSD's), but this might be due in part to the
different
locations of the instruments. The undamped instrument was on a
home-built 'pier'
in my home basement, whereas the VolksMeter was on the concrete-slab
floor of the
Willett Science Center here at Mercer University (about two miles from
my
house). The building may be hindered with respect to the tilts
occurring at the
longest periods. For you 'purists', note the fact that the
first-disturbance
arrival times of both P and S are abundantly clear, including the delta
time
between them--closely correlated with the 'proper' instrument, our
VolksMeter. I
expect similar results with an undamped, tuned garden-gate pendulum with
a period
5 times longer at 20 s--the big difference being that the surface waves
that
characterize the teleseismic earthquake record will be enhanced
significantly
because their frequencies are close to the high-Q resonance of the
instrument.
Randall
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Pendulum Q
From: ian ian@...........
Date: Sun, 21 Jan 2007 16:37:25 +0000
it would be interesting to compare signals from the same pendulum in a
damped and undamped state, for similar events, if the data is available.
Ian
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Shadow Zone
From: "tchannel" tchannel@..............
Date: Sun, 21 Jan 2007 10:39:32 -0700
Hi Folks, I did receive a nice recording of the 7.3M Molucca Sea, which =
was 108.5 degrees, 12063km from Boise Id.
I was under the impression that this event would not be visible as it =
fall between the 103 and the 143. The P and S shadow zones.
The P is very visible and the S? not sure. Could this be? or am I just =
seeing other things which I think are the P and the S?
Nice recording anyway. Thanks, Ted
Hi Folks, I did receive a nice =
recording of=20
the 7.3M Molucca Sea, which was 108.5 degrees, 12063km from Boise=20
Id.
I was under the impression that this =
event would=20
not be visible as it fall between the 103 and the 143. The P =
and S=20
shadow zones.
The P is very visible and the S? not=20
sure. Could this be? or am I just seeing other things which =
I think=20
are the P and the S?
Nice recording anyway. Thanks,=20
Ted
Subject: Re: Shadow Zone
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sun, 21 Jan 2007 17:46:00 +0000
Hi
I did also record the 7.2Mw event. But the P wave was delaed due to the
shadow zone. USGS has a map of P wave times and the shadow zone here,
http://neic.usgs.gov/neis/eq_depot/2007/eq_070121_xvam/neic_xvam_t.html
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Shadow Zone
From: "tchannel" tchannel@..............
Date: Sun, 21 Jan 2007 11:04:09 -0700
Perhaps, I am seeing the=20
Pdif (old:Pdiff) P diffracted along the CMB in the mantle =20
Using Winquake and the View/Phases/Display, I see the first part =
labeled "Pdiff" and no P or S labeled. This is my first event which was =
in the Shadow. Winquake is a Very nice tool. Thanks, Ted
Perhaps, I am seeing the
Pdif
(old:Pdiff) P diffracted along the CMB in the mantle=20
Using Winquake and the View/Phases/Display, I see the first =
part=20
labeled "Pdiff" and no P or S labeled. This is my first event =
which was in=20
the Shadow. Winquake is a Very nice tool. =
Thanks,=20
Ted
Subject: Pendulum Q
From: Roger Sparks rsparks@..........
Date: Sun, 21 Jan 2007 12:14:28 -0800
Good Morning All,
Of course removing the damper will improve the sensitivity of a
seismometer. Yes, it takes power to move a pendulum from the rest
position, and earthquakes provide that power. Once moving, the pendulum
is considered to have stored energy in the form of velocity (which is
measured in relation to stationary surroundings).
A pendulum will continue to receive energy from ongoing waves as time
passes, and the pendulum (if friction free and undamped) will integrate
the positive and negative motions into an instantaneous velocity. The
instantaneous velocity would be the sum of all the impulses over the
time period since the instrument was constructed (a very long time).
This is only true for an ideal pendulum.
An ideal pendulum can be digitally approximated easily from a damped
pendulum. This is done by summing all the readings from the moment of
first "switch on". This is not too practical.
More practical, we can recognize that even an undamped pendulum will
have friction from hinges, air and sensor interactions. It will have a
decay curve as the energy from an initial impulse is lost to friction.
The pendulum will also have a natural frequency which is constant for
any dimensionally stable system. Both the decay curve and pendulum
frequency can be modeled in software. Once modeled, the effect of each
discrete impulse can be subtracted from (or added to) the pendulum's
ongoing output signals. Assuming we are using velocity detector, the
subtracted result would be instantaneous acceleration, the added result
would be the displacement.
To use this method, the pendulum's period and Q would be critical
measurements. Any difference between the model and actual instrument
response would result in a digitally introduced error. In practice,
the errors should be small over the time periods of interest.
Larry has made available in Winquake a feature called "Integration".
The help file has the following for this function:
*/"Integrate Data Alt+I/*
Used to integrate the data set. Integration converts acceleration to
velocity and velocity to displacement."
This brings up a very important point--what is the pendulum sensor
reading? Is it acceleration, velocity, or displacement?
I need help here. I think we could make an acceleration detector with
a strain gage, which changed resistance under strain. Magnetic sensors
are all velocity detectors because they move through a changing magnetic
field. A capacitive detector is a displacement detector because the
output signal is the result of relative positions.
Back to Larry's integration feature. He seems to have anticipated at
least part of this discussion by providing the integration feature. By
integrating the signal over what ever time period desired, we accurately
model the output of an undamped pendulum. The only difference is that
about 1/2 the power of the earthquake signal is lost in the damping
system of the damped pendulum. This reduces the signal to noise ratio,
but only the noise from seismometer and electronics, not noise from the
actual seismic signal.
It is interesting to notice that the process of display can change the
character of the signal. For example, a displacement display would
represent the relative position on a chart. The larger the difference
in position, the larger the display difference. But the sensor must
have had an acceleration and velocity as it moved, so the display is
actually an integrated sum of the acceleration and velocity
components. The only thing that has really changed from velocity or
acceleration detection is that the phase of the displayed result has
changed in time. If acceleration or velocity is measured, we can
predict where we are going. If displacement is measured, we know where
we are at the instant of measurement.
Roger
*//*
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Pendulum Q
From: Bobhelenmcclure@.......
Date: Sun, 21 Jan 2007 17:06:25 EST
Randall Peters wrote:
Notice, Bob, what I said about the matter. If the 'purity' of the events is
not what you are most interested in, then give it a try. The 'carrier' (a
misnomer) you mention is not 20 Hz but 50 mHz (much lower frequency than body
wave values). There is useful information concerning the energy of the
earthquake by doing the power spectral density (corrected for the transfer
function of the instrument; i.e., the transient, or 'ringing' features)--
independent of the 'events'. My guess is that most people don't really use the details
of the event
information quantitatively anyway.
Hi Randall,
I guess I am not like "most people". I try very hard to keep my sensors
calibrated and as broadbanded as required to accurately sense and reproduce all
phases, and my timing within a fraction of a second. I am not particularly
interested in the L phases, except for estimating direction. If you look at my
Molucca Sea event file, 070121.114300.rem.psn, you will not find the extra
hour it took to receive the L waves.
Sorry, but I will not even think of trying what you suggest.
Nor am I interested in displacement sensing. I tried that a long time ago,
and all my dynamic range was used up by uncontrollable tilts and drift. If I
want to see displacement, I integrate my velocity data after high pass
filtering it with my own design zero lag filter to exclude signals lower than
0.025 Hz.
Bob
Randall Peters wrote:
Notice, Bob, what I said about the matter. If the 'purity' of the=
=20
events is not what you are most interested in, then give it a try. The=
=20
'carrier' (a misnomer) you mention is not 20 Hz but 50 mHz (much lower frequ=
ency=20
than body wave values). There is useful information concerning the ene=
rgy=20
of the earthquake by doing the power spectral density (corrected for the=20
transfer function of the instrument; i.e., the transient, or 'ringing'=20
features)-- independent of the 'events'. My guess is that most people=20
don't really use the details of the event information quantitatively=20
anyway.
Hi Randall,
I guess I am not like "most people". I try very hard to keep my=20
sensors calibrated and as broadbanded as required to accurately sense and=20
reproduce all phases, and my timing within a fraction of a second. I am=
not=20
particularly interested in the L phases, except for estimating direction. If=
you=20
look at my Molucca Sea event file, 070121.114300.rem.psn, you will not find=20=
the=20
extra hour it took to receive the L waves.
Sorry, but I will not even think of trying what you suggest.
Nor am I interested in displacement sensing. I tried that a long=
=20
time ago, and all my dynamic range was used up by uncontrollable tilts=20=
and=20
drift. If I want to see displacement, I integrate my velocity data after hig=
h=20
pass filtering it with my own design zero lag filter to exclude signals=
=20
lower than 0.025 Hz.
Bob
Subject: Re: Shadow Zone
From: Bobhelenmcclure@.......
Date: Sun, 21 Jan 2007 17:33:12 EST
The direct P phase is not detected beyond 103 degrees because it is in the
shadow of the core. There are phases which pass through the core. If you want
a good picture of how seismic waves propagate, try running the Seismic Waves
program by Alan Jones, _http://www.geol.binghamton.edu/faculty/jones/_
(http://www.geol.binghamton.edu/faculty/jones/)
I have a program "Travel Time" which might also be useful. It plots and
uses the Jeffreys and Bullen Seismological Tables to list the time of arrival of
an event at your station coordinates. Just enter your station coordinates,
and the event line from NEIC, load file "BigList.jb1, and you can get travel
and arrival times for all JB files listed to the clipboard, and a plot of all
phases for all distances. The program can be downloaded from:
_http://www.jclahr.com/science/psn/mcclure/traveltime/index.html_
(http://www.jclahr.com/science/psn/mcclure/traveltime/index.html)
For a discussion of some special core waves, consult
_http://www.seismosoc.org/publications/SRL/SRL_72/srl_72-1_eq.html_
(http://www.seismosoc.org/publications/SRL/SRL_72/srl_72-1_eq.html)
Hope this is helpful
Bob
The direct P phase is not detected beyond 103 degrees because it=
is=20
in the shadow of the core. There are phases which pass through the core. If=20=
you=20
want a good picture of how seismic waves propagate, try running the Sei=
smic=20
Waves program by Alan Jones, http://www.geol.bingh=
amton.edu/faculty/jones/
I have a program "Travel Time" which might also be useful. It pl=
ots=20
and uses the Jeffreys and Bullen Seismological Tables to list the time of arriva=
l of=20
an event at your station coordinates. Just enter your station coordinates, a=
nd=20
the event line from NEIC, load file "BigList.jb1, and you can get trave=
l=20
and arrival times for all JB files listed to the clipboard, and a plot of al=
l=20
phases for all distances. The program can be downloaded from:
Subject: Re: Pendulum Q
From: ChrisAtUpw@.......
Date: Sun, 21 Jan 2007 19:05:43 EST
In a message dated 21/01/2007, Bobhelenmcclure@....... writes:
Sorry, but I will not even think of trying what you suggest.
Hi Bob,
Entirely your choice! But don't discourage others from experimenting.
Nor am I interested in displacement sensing. I tried that a long time ago,
and all my dynamic range was used up by uncontrollable tilts and drift.
Which could have told you quite a lot about your equipment and how to
improve it?
Try LVDT or capacitative detectors some time? You might like one of them!
My LVDT seems to work fine. Professional systems tend to use
capacitative types.
Regards,
Chris Chapman
In a message dated 21/01/2007, Bobhelenmcclure@....... writes:
Nor am I interested in displacement sensing. I tried that a lo=
ng=20
time ago, and all my dynamic range was used up by uncontrollable tilt=
s=20
and drift.
Which could have told you quite a lot about you=
r=20
equipment and how to improve it?
Try LVDT or capacitative detectors some time? Y=
ou=20
might like one of them!
My LVDT seems to work fine. Professional system=
s=20
tend to use capacitative types.
Regards,
Chris Chapman
Subject: Molucca Sea Earthquake
From: "Michael Kimzey" mckimzey@...........
Date: Sun, 21 Jan 2007 22:24:17 -0500
Hi all.
Very good discussions here on the list. I just recorded my very first
earthquake and am HOOKED! Totally incredible that this thing of plumbing
supplies and magnets could pick up vibrations from across the world.
Ok...some questions, especially because I would like to share this data if
anyone wants it.
1) is there someplace (FAQ or such) that directs how to set up the alarms in
WinSDR?
2) What should I do with the .psn file if others want it (do I send it to
somebody?)
On my system, the waves could be seen on the graph for 90 minutes, is this
normal or is my Lehman underdamped?
Thanks for any feedback or links to FAQ's that I missed.
PS, if there is anyone that has one of Larry's SG electronics boards that
they want to part with, please email me directly.
- Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Digest from 01/21/2007 00:00:40
From: Randall Peters PETERS_RD@..........
Date: Mon, 22 Jan 2007 09:47:19 -0500
Roger, I have respnded to your request for help; i.e.,
"This brings up a very important point--what is the pendulum sensor
reading? Is it acceleration, velocity, or displacement? I need help here. "
With all the confusion as to how a seismometer functions, one has to wonder if Einstein was
the only one who ever acquired a complete conceptual
mastery of inertia. His principle of relativity states that the ``laws of physics remain the
same for any non-accelerating frame of reference''. In
practical terms, this equivalence of inertial reference frames means that it is impossible
to detect uniform motion on the basis of measurements
conducted inside a box, such as a seismometer. Thus the only feature of motion having any
importance whatsoever to a seismometer is acceleration
of the case that supports its inertial mass M. It is very common to erroneously believe that
any type motion of the case will be met with displacement
of M relative to the case, because of the inertia of M. Be sure to understand that the only
property of the motion that is ``resisted'' by M is the
acceleration. Thus the acceleration is the only thing that can be directly measured!!
Velocity and position, the other kinematic variables so frequently
discussed in seismology, can only be inferred from the acceleration measurement. Unlike the
quintessential acceleration, they cannot be directly
measured, even though they are frequently specified.
The output from a seismometer is directly proportional to acceleration, as long as the
acceleration takes place at a frequency
lower than the natural (eigen) frequency of the instrument, and additionally, it is
operating with damping that is near critical. When the frequency of
the drive is higher than the natural frequency of the instrument, the response of the
instrument is attenuated by the ratio of the square of the drive
frequency to the square of the eigenfrequency. If one is talking about the ground
displacement, as opposed to the acceleration, just the opposite
behavior is found. For those who want to believe that a seismometer responds directly to
ground displacement, complete confusion results.
It is also important to note that the horizontal seismometer, such as a pendulum,
responds to more than one type of acceleration. From ``inside the
box'' of the instrument there is no way to distinguish between these two forms of
acceleration, which are (i) horizontal acceleration of the instrument,
and (ii) changes in orientation of the box (tilt) relative to the direction of the local
field of the earth g of the earth, having the magnitude of 9.8 m/s2.
Randall
psn-l-digest-request@.............. wrote:
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 1 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: RE: Pendulum Q
> From: "Stephen Hammond"
> Date: Sun, 21 Jan 2007 00:40:20 -0800
>
> Boy, this is getting a little mixed up. Are we talking about the
> response of the instrument or the site response of the recording
> location?
> Regards, Steve Hammond PSN San Jose, Aptos Ca.
>
> -----Original Message-----
> From: psn-l-request@.............. [mailto:psn-l-request@...............
> On Behalf Of Larry Cochrane
> Sent: Saturday, January 20, 2007 10:52 PM
> To: psn-l@..............
> Subject: Re: Pendulum Q
>
> From Randall. -Larry
>
> Notice, Bob, what I said about the matter. If the 'purity' of the
> events is not
> what you are most interested in, then give it a try. The 'carrier' (a
> misnomer)
> you mention is not 20 Hz but 50 mHz (much lower frequency than body wave
> values). There is useful information concerning the energy of the
> earthquake by
> doing the power spectral density (corrected for the transfer function of
> the
> instrument; i.e., the transient, or 'ringing' features)-- independent of
> the
> 'events'. My guess is that most people don't really use the details of
> the event
> information quantitatively anyway. You go find out where the earthquake
> occurred
> by consulting USGS webpages after you've seen it on your seismograph.
> It is not
> the time difference between P and S events that serves as the primary
> means for
> locating an earthquake by USGS anyway. The errors of a calculation
> based on the
> difference in speeds of the longitudinal and transverse components are
> much worse
> than a calculation using only the P event from two or more instruments
> geographically separated in azimuth by a large amount relative to the
> earthquake. In other words, USGS uses triangulation as the means for
> localizing
> earthquakes. Yes it is nice to observe the S wave delay relative to the
> P wave
> as a rough measure of how far away the earthquake was. I figured,
> however, that
> some of you would like to just 'see' the surface waves from weaker,
> distant
> earthquakes. I predict that by the means I mentioned you will see some
> of them
> that otherwise would go unnoticed. Before anybody makes sweeping
> generalizations
> about my heresy, I suggest that you first take a look at the graphs that
> I have
> posted on my webpage at http://physics.mercer.edu/hpage/listserve.gif
> It shows
> that the undamped pendulum (in spite of ringing, following arrival of
> each of the
> P and S waves for the case shown-- nevertheless contains decent
> information
> concerning the spectral features of the most important piece of the
> record; i.e.,
> the surface waves, whose frequencies are distributed between
> approximately 7 s
> and 70 s. The very longest periods differ between the VolksMeter record
> and the
> undamped pendulum record (PSD's), but this might be due in part to the
> different
> locations of the instruments. The undamped instrument was on a
> home-built 'pier'
> in my home basement, whereas the VolksMeter was on the concrete-slab
> floor of the
> Willett Science Center here at Mercer University (about two miles from
> my
> house). The building may be hindered with respect to the tilts
> occurring at the
> longest periods. For you 'purists', note the fact that the
> first-disturbance
> arrival times of both P and S are abundantly clear, including the delta
> time
> between them--closely correlated with the 'proper' instrument, our
> VolksMeter. I
> expect similar results with an undamped, tuned garden-gate pendulum with
> a period
> 5 times longer at 20 s--the big difference being that the surface waves
> that
> characterize the teleseismic earthquake record will be enhanced
> significantly
> because their frequencies are close to the high-Q resonance of the
> instrument.
>
> Randall
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 2 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Pendulum Q
> From: ian
> Date: Sun, 21 Jan 2007 16:37:25 +0000
>
> it would be interesting to compare signals from the same pendulum in a
> damped and undamped state, for similar events, if the data is available.
>
> Ian
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 3 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Shadow Zone
> From: "tchannel"
> Date: Sun, 21 Jan 2007 10:39:32 -0700
>
> This is a multi-part message in MIME format.
>
> ------=_NextPart_000_0057_01C73D48.70008390
> Content-Type: text/plain;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
> Hi Folks, I did receive a nice recording of the 7.3M Molucca Sea, which =
> was 108.5 degrees, 12063km from Boise Id.
> I was under the impression that this event would not be visible as it =
> fall between the 103 and the 143. The P and S shadow zones.
> The P is very visible and the S? not sure. Could this be? or am I just =
> seeing other things which I think are the P and the S?
> Nice recording anyway. Thanks, Ted
> ------=_NextPart_000_0057_01C73D48.70008390
> Content-Type: text/html;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
>
>
> charset=3Diso-8859-1">
>
>
>
>
>
Hi Folks, I did receive a nice =
> recording of=20
> the 7.3M Molucca Sea, which was 108.5 degrees, 12063km from Boise=20
> Id.
>
I was under the impression that this =
> event would=20
> not be visible as it fall between the 103 and the 143. The P =
> and S=20
> shadow zones.
>
The P is very visible and the S? not=20
> sure. Could this be? or am I just seeing other things which =
> I think=20
> are the P and the S?
>
Nice recording anyway. Thanks,=20
> Ted
>
> ------=_NextPart_000_0057_01C73D48.70008390--
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 4 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Shadow Zone
> From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?=
> Date: Sun, 21 Jan 2007 17:46:00 +0000
>
> Hi
>
> I did also record the 7.2Mw event. But the P wave was delaed due to the
> shadow zone. USGS has a map of P wave times and the shadow zone here,
> http://neic.usgs.gov/neis/eq_depot/2007/eq_070121_xvam/neic_xvam_t.html
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 5 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Shadow Zone
> From: "tchannel"
> Date: Sun, 21 Jan 2007 11:04:09 -0700
>
> This is a multi-part message in MIME format.
>
> ------=_NextPart_000_0076_01C73D4B.DFFFE700
> Content-Type: text/plain;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
> Perhaps, I am seeing the=20
> Pdif (old:Pdiff) P diffracted along the CMB in the mantle =20
>
> Using Winquake and the View/Phases/Display, I see the first part =
> labeled "Pdiff" and no P or S labeled. This is my first event which was =
> in the Shadow. Winquake is a Very nice tool. Thanks, Ted
> ------=_NextPart_000_0076_01C73D4B.DFFFE700
> Content-Type: text/html;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
>
>
> charset=3Diso-8859-1">
>
>
>
>
>
Perhaps, I am seeing the
>
>
>
>
>
Pdif
>
(old:Pdiff) P diffracted along the CMB in the mantle=20
>
>
Using Winquake and the View/Phases/Display, I see the first =
> part=20
> labeled "Pdiff" and no P or S labeled. This is my first event =
> which was in=20
> the Shadow. Winquake is a Very nice tool. =
> Thanks,=20
> Ted
>
> ------=_NextPart_000_0076_01C73D4B.DFFFE700--
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 6 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Pendulum Q
> From: Roger Sparks
> Date: Sun, 21 Jan 2007 12:14:28 -0800
>
> Good Morning All,
>
> Of course removing the damper will improve the sensitivity of a
> seismometer. Yes, it takes power to move a pendulum from the rest
> position, and earthquakes provide that power. Once moving, the pendulum
> is considered to have stored energy in the form of velocity (which is
> measured in relation to stationary surroundings).
>
> A pendulum will continue to receive energy from ongoing waves as time
> passes, and the pendulum (if friction free and undamped) will integrate
> the positive and negative motions into an instantaneous velocity. The
> instantaneous velocity would be the sum of all the impulses over the
> time period since the instrument was constructed (a very long time).
> This is only true for an ideal pendulum.
>
> An ideal pendulum can be digitally approximated easily from a damped
> pendulum. This is done by summing all the readings from the moment of
> first "switch on". This is not too practical.
>
> More practical, we can recognize that even an undamped pendulum will
> have friction from hinges, air and sensor interactions. It will have a
> decay curve as the energy from an initial impulse is lost to friction.
> The pendulum will also have a natural frequency which is constant for
> any dimensionally stable system. Both the decay curve and pendulum
> frequency can be modeled in software. Once modeled, the effect of each
> discrete impulse can be subtracted from (or added to) the pendulum's
> ongoing output signals. Assuming we are using velocity detector, the
> subtracted result would be instantaneous acceleration, the added result
> would be the displacement.
>
> To use this method, the pendulum's period and Q would be critical
> measurements. Any difference between the model and actual instrument
> response would result in a digitally introduced error. In practice,
> the errors should be small over the time periods of interest.
>
> Larry has made available in Winquake a feature called "Integration".
> The help file has the following for this function:
>
> */"Integrate Data Alt+I/*
>
> Used to integrate the data set. Integration converts acceleration to
> velocity and velocity to displacement."
>
> This brings up a very important point--what is the pendulum sensor
> reading? Is it acceleration, velocity, or displacement?
>
> I need help here. I think we could make an acceleration detector with
> a strain gage, which changed resistance under strain. Magnetic sensors
> are all velocity detectors because they move through a changing magnetic
> field. A capacitive detector is a displacement detector because the
> output signal is the result of relative positions.
>
> Back to Larry's integration feature. He seems to have anticipated at
> least part of this discussion by providing the integration feature. By
> integrating the signal over what ever time period desired, we accurately
> model the output of an undamped pendulum. The only difference is that
> about 1/2 the power of the earthquake signal is lost in the damping
> system of the damped pendulum. This reduces the signal to noise ratio,
> but only the noise from seismometer and electronics, not noise from the
> actual seismic signal.
>
> It is interesting to notice that the process of display can change the
> character of the signal. For example, a displacement display would
> represent the relative position on a chart. The larger the difference
> in position, the larger the display difference. But the sensor must
> have had an acceleration and velocity as it moved, so the display is
> actually an integrated sum of the acceleration and velocity
> components. The only thing that has really changed from velocity or
> acceleration detection is that the phase of the displayed result has
> changed in time. If acceleration or velocity is measured, we can
> predict where we are going. If displacement is measured, we know where
> we are at the instant of measurement.
>
> Roger
>
> *//*
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 7 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Pendulum Q
> From: Bobhelenmcclure@.......
> Date: Sun, 21 Jan 2007 17:06:25 EST
>
> -------------------------------1169417185
> Content-Type: text/plain; charset="US-ASCII"
> Content-Transfer-Encoding: 7bit
>
> Randall Peters wrote:
>
> Notice, Bob, what I said about the matter. If the 'purity' of the events is
> not what you are most interested in, then give it a try. The 'carrier' (a
> misnomer) you mention is not 20 Hz but 50 mHz (much lower frequency than body
> wave values). There is useful information concerning the energy of the
> earthquake by doing the power spectral density (corrected for the transfer
> function of the instrument; i.e., the transient, or 'ringing' features)--
> independent of the 'events'. My guess is that most people don't really use the details
> of the event
> information quantitatively anyway.
>
> Hi Randall,
>
> I guess I am not like "most people". I try very hard to keep my sensors
> calibrated and as broadbanded as required to accurately sense and reproduce all
> phases, and my timing within a fraction of a second. I am not particularly
> interested in the L phases, except for estimating direction. If you look at my
> Molucca Sea event file, 070121.114300.rem.psn, you will not find the extra
> hour it took to receive the L waves.
>
> Sorry, but I will not even think of trying what you suggest.
>
> Nor am I interested in displacement sensing. I tried that a long time ago,
> and all my dynamic range was used up by uncontrollable tilts and drift. If I
> want to see displacement, I integrate my velocity data after high pass
> filtering it with my own design zero lag filter to exclude signals lower than
> 0.025 Hz.
>
> Bob
>
> -------------------------------1169417185
> Content-Type: text/html; charset="US-ASCII"
> Content-Transfer-Encoding: quoted-printable
>
>
>
>
>
> Arial"=20
> bottomMargin=3D7 leftMargin=3D7 topMargin=3D7 rightMargin=3D7> e_document=20
> face=3DArial color=3D#000000 size=3D2> color=3D#000000=20
> size=3D2> T=20
> id=3Drole_document face=3DArial color=3D#000000 size=3D2> ument=20
> face=3DArial color=3D#000000 size=3D2>
>
Randall Peters wrote:
>
>
Notice, Bob, what I said about the matter. If the 'purity' of the=
> =20
> events is not what you are most interested in, then give it a try. The=
> =20
> 'carrier' (a misnomer) you mention is not 20 Hz but 50 mHz (much lower frequ=
> ency=20
> than body wave values). There is useful information concerning the ene=
> rgy=20
> of the earthquake by doing the power spectral density (corrected for the=20
> transfer function of the instrument; i.e., the transient, or 'ringing'=20
> features)-- independent of the 'events'. My guess is that most people=20
> don't really use the details of the event information quantitatively=20
> anyway.
>
>
Hi Randall,
>
>
I guess I am not like "most people". I try very hard to keep my=20
> sensors calibrated and as broadbanded as required to accurately sense and=20
> reproduce all phases, and my timing within a fraction of a second. I am=
> not=20
> particularly interested in the L phases, except for estimating direction. If=
> you=20
> look at my Molucca Sea event file, 070121.114300.rem.psn, you will not find=20=
> the=20
> extra hour it took to receive the L waves.
>
>
Sorry, but I will not even think of trying what you suggest. V>
>
>
Nor am I interested in displacement sensing. I tried that a long=
> =20
> time ago, and all my dynamic range was used up by uncontrollable tilts=20=
> and=20
> drift. If I want to see displacement, I integrate my velocity data after hig=
> h=20
> pass filtering it with my own design zero lag filter to exclude signals=
> =20
> lower than 0.025 Hz.
>
>
Bob
>
> -------------------------------1169417185--
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 8 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Shadow Zone
> From: Bobhelenmcclure@.......
> Date: Sun, 21 Jan 2007 17:33:12 EST
>
> -------------------------------1169418792
> Content-Type: text/plain; charset="US-ASCII"
> Content-Transfer-Encoding: 7bit
>
> The direct P phase is not detected beyond 103 degrees because it is in the
> shadow of the core. There are phases which pass through the core. If you want
> a good picture of how seismic waves propagate, try running the Seismic Waves
> program by Alan Jones, _http://www.geol.binghamton.edu/faculty/jones/_
> (http://www.geol.binghamton.edu/faculty/jones/)
>
> I have a program "Travel Time" which might also be useful. It plots and
> uses the Jeffreys and Bullen Seismological Tables to list the time of arrival of
> an event at your station coordinates. Just enter your station coordinates,
> and the event line from NEIC, load file "BigList.jb1, and you can get travel
> and arrival times for all JB files listed to the clipboard, and a plot of all
> phases for all distances. The program can be downloaded from:
>
> _http://www.jclahr.com/science/psn/mcclure/traveltime/index.html_
> (http://www.jclahr.com/science/psn/mcclure/traveltime/index.html)
>
> For a discussion of some special core waves, consult
>
> _http://www.seismosoc.org/publications/SRL/SRL_72/srl_72-1_eq.html_
> (http://www.seismosoc.org/publications/SRL/SRL_72/srl_72-1_eq.html)
>
> Hope this is helpful
>
> Bob
>
> -------------------------------1169418792
> Content-Type: text/html; charset="US-ASCII"
> Content-Transfer-Encoding: quoted-printable
>
>
>
>
>
> Arial"=20
> bottomMargin=3D7 leftMargin=3D7 topMargin=3D7 rightMargin=3D7> e_document=20
> face=3DArial color=3D#000000 size=3D2>
>
The direct P phase is not detected beyond 103 degrees because it=
> is=20
> in the shadow of the core. There are phases which pass through the core. If=20=
> you=20
> want a good picture of how seismic waves propagate, try running the Sei=
> smic=20
> Waves program by Alan Jones, href=3D"http://www.geol.binghamton.edu/faculty/jones/">http://www.geol.bingh=
> amton.edu/faculty/jones/
>
>
I have a program "Travel Time" which might also be useful. It pl=
> ots=20
> and uses the Jeffreys and class=3DSpellE>Bullen Seismological Tables to list the time of arriva=
> l of=20
> an event at your station coordinates. Just enter your station coordinates, a=
> nd=20
> the event line from NEIC, load file "BigList.jb1, and you can get trave=
> l=20
> and arrival times for all JB files listed to the clipboard, and a plot of al=
> l=20
> phases for all distances. The program can be downloaded from:
>
> -------------------------------1169418792--
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 9 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Pendulum Q
> From: ChrisAtUpw@.......
> Date: Sun, 21 Jan 2007 19:05:43 EST
>
> -------------------------------1169424343
> Content-Type: text/plain; charset="US-ASCII"
> Content-Transfer-Encoding: 7bit
>
> In a message dated 21/01/2007, Bobhelenmcclure@....... writes:
>
> Sorry, but I will not even think of trying what you suggest.
>
> Hi Bob,
>
> Entirely your choice! But don't discourage others from experimenting.
>
> Nor am I interested in displacement sensing. I tried that a long time ago,
> and all my dynamic range was used up by uncontrollable tilts and drift.
>
> Which could have told you quite a lot about your equipment and how to
> improve it?
> Try LVDT or capacitative detectors some time? You might like one of them!
> My LVDT seems to work fine. Professional systems tend to use
> capacitative types.
>
> Regards,
>
> Chris Chapman
>
> -------------------------------1169424343
> Content-Type: text/html; charset="US-ASCII"
> Content-Transfer-Encoding: quoted-printable
>
>
>
>
>
> Arial"=20
> bottomMargin=3D7 leftMargin=3D7 topMargin=3D7 rightMargin=3D7> e_document=20
> face=3DArial color=3D#000000 size=3D2>
>
In a message dated 21/01/2007, Bobhelenmcclure@....... writes:
Nor am I interested in displacement sensing. I tried that a lo=
> ng=20
> time ago, and all my dynamic range was used up by uncontrollable tilt=
> s=20
> and drift.
>
>
Which could have told you quite a lot about you=
> r=20
> equipment and how to improve it?
>
Try LVDT or capacitative detectors some time? Y=
> ou=20
> might like one of them!
>
My LVDT seems to work fine. Professional system=
> s=20
> tend to use capacitative types.
>
>
Regards,
>
>
Chris Chapman
>
> -------------------------------1169424343--
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 10 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Molucca Sea Earthquake
> From: "Michael Kimzey"
> Date: Sun, 21 Jan 2007 22:24:17 -0500
>
> Hi all.
>
> Very good discussions here on the list. I just recorded my very first
> earthquake and am HOOKED! Totally incredible that this thing of plumbing
> supplies and magnets could pick up vibrations from across the world.
>
> Ok...some questions, especially because I would like to share this data if
> anyone wants it.
> 1) is there someplace (FAQ or such) that directs how to set up the alarms in
> WinSDR?
> 2) What should I do with the .psn file if others want it (do I send it to
> somebody?)
>
> On my system, the waves could be seen on the graph for 90 minutes, is this
> normal or is my Lehman underdamped?
>
> Thanks for any feedback or links to FAQ's that I missed.
>
> PS, if there is anyone that has one of Larry's SG electronics boards that
> they want to part with, please email me directly.
>
> - Mike
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-DIGEST-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
Subject: Re: Capacitive Detectors
From: ChrisAtUpw@.......
Date: Mon, 22 Jan 2007 12:58:21 EST
In a message dated 22/01/2007, gpayton880@....... writes:
Chris, where may I find more information on the capacitive detectors,
please. And, what is "LVDT?"
Hi Jerry,
Have a look at
_http://mysite.verizon.net/ressczez/homebuilt_seismometers/_ (http://mysite.verizon.net/ressczez/homebuilt_seismometers/) for a good
capacitative sensor design. There are two basic sorts. In gap varying sensors,
you have a central electrode which can move between two outside pickup
electrodes. The charge coupled to the electrodes depends on the plate separation.
There are direct and capacitance bridge designs. The direct resonant design
used on the SG sensor is moderately temperature dependant see
_http://psn.quake.net/sgboard.html_ (http://psn.quake.net/sgboard.html) Other direct designs
are available with phase sensitive detector outputs, a high sensitivity and
very low drifts. Half bridge designs may be used to give a high rejection to
stray capacitances / external fields. The linear range is small, maybe +/-2mm
max. These are often used on force feedback systems.
Another arrangement uses two fixed parallel plates, edge on, with a
moving plate of half the total width partially overlapping them. The capacity of
the moving plate to the each fixed plate varies linearly with position - a
differential plate capacitor (also butterfly rotational type). The linear range
of these can be much greater.
However, you can also use linear movement / parallel shield plate
design. See Professor Peters' description at
_http://physics.mercer.edu/petepag/tutorial.html_ (http://physics.mercer.edu/petepag/tutorial.html) This consists
of two static outside plates and one central moving plate. One static plate
has two longitudinal conducting strips excited by an oscillator. The opposite
static plate uses four sense electrodes which are cross coupled. The moving
electrode has 1/2 the length of the excited strip. This acts as an earthed
shield electrode although no earth contact is required. As the shield electrode
moves, the phase of the charge coupled to the plates varies. This is amplified
differentially and put into a phase sensitive detector. The length /
movement range can be varied at will. For relatively small movements, you can use a
long drive electrode and several parallel coupled four electrode sensor
cells. An arrangement of parallel strips is then used for the moving electrode.
Rotational and moving diaphragm types can also be used.
A LVDT is a Linear Variable Differential Transformer. You have an AC
excited central coil winding and also two outside pickup coils connected in
series / opposition on the same axis. A soft magnetic armature can move along the
central axis. It is magnetised by the central coil, but the fraction of the
field coupled to the end pickup coils depends upon the armature position.
Phase sensitive detectors are usually used. A good example is shown at
_http://www.keckec.com/seismo/_ (http://www.keckec.com/seismo/) You can either wind
or buy the sensor coils + armature. If you buy, look for a 'free armature'
model. My system gives a +/-6mm range with a +/-7 nano metre noise floor. At
+/-10 mm, it is 10% down in sensitivity.
Another inductive type uses a variable reluctance sensor made from
miniature audio transformers eg from Mouser. See
_http://www.eas.slu.edu/People/STMorrissey/_ (http://www.eas.slu.edu/People/STMorrissey/) Again, this type has
a high sensitivity, but a small linear range and may be used with force
feedback systems.
Hope that this helps,
Chris Chapman
In a message dated 22/01/2007, gpayton880@....... writes:
Chris, where may I find more information on the capacitive=20
detectors, please. And, what is=20
"LVDT?"
Hi Jerry,
Have a look at http://m=
ysite.verizon.net/ressczez/homebuilt_seismometers/ for=20
a good capacitative sensor design. There are two basic sorts. In gap varying=
=20
sensors, you have a central electrode which can move between two outside pic=
kup=20
electrodes. The charge coupled to the electrodes depends on the plate=20
separation. There are direct and capacitance bridge designs. The direct=20
resonant design used on the SG sensor is moderately temperature=20
dependant see http://psn.quake.net/sgboard.html=
Other=20
direct designs are available with phase sensitive detector outputs, a high=20
sensitivity and very low drifts. Half bridge designs may be used to giv=
e a=20
high rejection to stray capacitances / external fields. The linear range is=20
small, maybe +/-2mm max. These are often used on force feedback systems.
Another arrangement uses two fixed parallel pla=
tes,=20
edge on, with a moving plate of half the total width partially overlapping t=
hem.=20
The capacity of the moving plate to the each fixed plate varies linearly wit=
h=20
position - a differential plate capacitor (also butterfly rotational type).=20
The linear range of these can be much greater.
However, you can also use linear movement=20=
/=20
parallel shield plate design. See Professor Peters' description at http://physics.merc=
er.edu/petepag/tutorial.html This=20
consists of two static outside plates and one central moving plate. One=
=20
static plate has two longitudinal conducting strips excited by an oscillator=
..=20
The opposite static plate uses four sense electrodes which are cross coupled=
..=20
The moving electrode has 1/2 the length of the excited strip. This=
=20
acts as an earthed shield electrode although no earth contact is required. A=
s=20
the shield electrode moves, the phase of the charge coupled to the=
=20
plates varies. This is amplified differentially and put into a phase sensiti=
ve=20
detector. The length / movement range can be varied at will. For relatively=20
small movements, you can use a long drive electrode and several paralle=
l=20
coupled four electrode sensor cells. An arrangement of parallel=20
strips is then used for the moving electrode. Rotational and moving=20
diaphragm types can also be used.
A LVDT is a Linear Variable Differential=20
Transformer. You have an AC excited central coil winding and also=20=
two=20
outside pickup coils connected in series / opposition on the same axis. A so=
ft=20
magnetic armature can move along the central axis. It is magnetised by the=20
central coil, but the fraction of the field coupled to the end pickup coils=20
depends upon the armature position. Phase sensitive detectors are usually us=
ed.=20
A good example is shown at http://www.keckec.com/seismo/&nbs=
p;You=20
can either wind or buy the sensor coils + armature. If you buy, look for a '=
free=20
armature' model. My system gives a +/-6mm range with a +/-7 nano metre noise=
=20
floor. At +/-10 mm, it is 10% down in sensitivity.
Another inductive type uses a variable=20
reluctance sensor made from miniature audio transformers eg from Mouser. See=
http://www.eas.slu.edu/P=
eople/STMorrissey/ Again,=20
this type has a high sensitivity, but a small linear range and may be used w=
ith=20
force feedback systems.
Hope that this helps,
Chris Chapman
Subject: Re: Capacitive Detectors
From: Ben Bradley benbradley@...............
Date: Mon, 22 Jan 2007 14:34:48 -0500
ChrisAtUpw@....... wrote:
>
> In a message dated 22/01/2007, gpayton880@....... writes:
>
>
> Chris, where may I find more information on the capacitive detectors,
This device which was recently discussed here uses a capacitive
detector:
http://psn.quake.net/volksmeter/State-of-the-art_Digital_Seismograph.pdf
This page has info on the IC connected to the capacitive sensor:
http://www.analog.com/en/prod/0%2C2877%2CAD7745%2C00.html
> please. And, what is "LVDT?"
It's a linear variable differential transformer, three coils wound
around a form with a magnetic core that moves within them. With proper
circuitry it gives a voltage proportional to the position of the core.
This page describes an LVDT:
http://www.keckec.com/seismo/
I've also seen an LVDT designed and used in the LIGO project that
uses only the three coils, with the center coil mounted on the moving
member to replace the moving magnetic core. One advantage of this is
there is no (or much less) "pull" on the moving part by magnetic
induction from the excitation coil.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Updated version of "Interpreting Seismograms"
From: John or Jan Lahr JohnJan@........
Date: Mon, 22 Jan 2007 11:40:35 -0800
Larry Braile has revised his tutorial for seismogram
interpretation. It's aimed at teachers using an AS-1 seismometer
with AmaSeis software, but this is an excellent source of information
for PSN members as well.
John
At 04:47 AM 1/22/2007, you wrote:
>An updated version of "Interpreting Seismograms -- A Tutorial for
>the AS-1 Seismograph" is available at:
>http://web.ics.purdue.edu/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm.
>You can also link to MS Word and PDF versions for convenient
>printing. Please let me know if you have comments or
>suggestions. I hope that the tutorial will be useful to AS-1 and
>other educational seismograph operators.
>
>-Larry Braile
>
>--
>Lawrence W. Braile, Professor and Head
>Department of Earth and Atmospheric Sciences
>550 Stadium Mall Drive
>Purdue University
>West Lafayette, IN 47907-2051
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Updated version of "Interpreting Seismograms"
From: "Thomas Dick" dickthomas01@.............
Date: Mon, 22 Jan 2007 14:40:55 -0600
John URL is found
----- Original Message -----
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Updated version of "Interpreting Seismograms"
From: "Thomas Dick" dickthomas01@.............
Date: Mon, 22 Jan 2007 14:48:59 -0600
The requested URL
/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm>http://web.ics.purdue.edu/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm.
was not found on this server.
----- Original Message -----
From: "John or Jan Lahr"
To:
Sent: Monday, January 22, 2007 1:40 PM
Subject: Updated version of "Interpreting Seismograms"
> Larry Braile has revised his tutorial for seismogram interpretation. It's
> aimed at teachers using an AS-1 seismometer with AmaSeis software, but
> this is an excellent source of information for PSN members as well.
>
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Updated version of "Interpreting Seismograms"
From: "Jerry Payton" gpayton880@.......
Date: Mon, 22 Jan 2007 15:02:44 -0600
This is the correct URL:
http://web.ics.purdue.edu/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm
The former was two URL's end-to-end. It needed to be edited.
Regards,
Jerry
----- Original Message -----
From: Thomas Dick
To: psn-l@..............
Sent: Monday, January 22, 2007 2:48 PM
Subject: Re: Updated version of "Interpreting Seismograms"
The requested URL
/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm>http://web.ics.purdue.edu/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm.
was not found on this server.
----- Original Message -----
From: "John or Jan Lahr"
To:
Sent: Monday, January 22, 2007 1:40 PM
Subject: Updated version of "Interpreting Seismograms"
> Larry Braile has revised his tutorial for seismogram interpretation.
It's
> aimed at teachers using an AS-1 seismometer with AmaSeis software, but
> this is an excellent source of information for PSN members as well.
>
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
To leave this list email PSN-L-REQUEST@.............. with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.
This is the correct URL: http://web.ics.purdue.edu/~braile/edumod/as1lessons/InterpS=
eis/InterpSeis.htm
The former was two URL's end-to-end. It needed to be =
edited.
Subject: Re: Updated version of =
"Interpreting Seismograms"
The requested URL=20
=
/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm>http://web.ic=
s.purdue.edu/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm.=20
was not found on this server. ----- Original Message ----- =
From:=20
"John or Jan Lahr" <JohnJan@........> To: =
<psn-l@..............> Sent=
:=20
Monday, January 22, 2007 1:40 PM Subject: Updated version of =
"Interpreting=20
Seismograms"
> Larry Braile has revised his tutorial for =
seismogram interpretation. It's > aimed at teachers using =
an AS-1=20
seismometer with AmaSeis software, but > this is an excellent =
source of=20
information for PSN members as well. > >=20
=
__________________________________________________________ Public=20
Seismic Network Mailing List (PSN-L)
To leave this list email =
PSN-L-REQUEST@...............
=20
with the body of the message (first line only): unsubscribe See =
http://www.seismicnet.co=
m/maillist.html=20
for more information.
Subject: Re: Updated version of "Interpreting Seismograms"
From: John or Jan Lahr JohnJan@........
Date: Mon, 22 Jan 2007 14:19:01 -0800
Good. I usually forget to include the URL, so am happy that I did
and that it works!
John
At 12:40 PM 1/22/2007, you wrote:
>John URL is found
>----- Original Message -----
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with the body
>of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Possible magma movement
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Mon, 22 Jan 2007 23:03:48 +0000
Hi all
I am seeing what I think is movement of magma (it is hard to tell at
this moment). I did notice a change in the IMO tremor plots at three
stations now. So far there are no earthquakes because of this magma
movement. But there is a clear change in the tremor plot on 0.5 - 2Hz
range. If that is any indication, it is clear that the magma has not
reached the surfice yet.
The change in the plot can be seen on Vatsfell tremor plot and
Skrokkalda tremor plot.
http://hraun.vedur.is/ja/englishweb/tremor.html
http://hraun.vedur.is/ja/oroi/vat.gif - Clearest signal.
http://hraun.vedur.is/ja/oroi/skr.gif - Signal appears.
This might be false alarm, but only time can tell if that is the case or
not. If magma is riseing, it is only matter of time until earthquake
starts to appear.
I've will keep this updated if anything intresting starts to happen.
Please send questions if you have them.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Sensor Type (was Pendulum Q)
From: Roger Sparks rsparks@..........
Date: Mon, 22 Jan 2007 23:08:01 -0800
Randle, Thanks for the thought provoking response.
I can understand what you are saying about direct coupled sensing of
pendulums, but I think I am correct in saying that your comments are
limited to sensors that actually extract some power from the pendulum
motion. A sensing system that (for instance) that counted area
sweeping past a camera in a time period should not count as a direct
coupled sensor.
I am using a magnetic/coil sensing system with a heavy damper. The
system is near or even more than critically damped. My sensing magnet
and coil are not providing much load on the pendulum, most of the energy
captured by the pendulum is dissipated in the damper. I certainly
agree that my sensing system is really acceleration based as it does
load and reduce the pendulum speed. The sensor also acts to accelerate
the pendulum from a standing start when a wave arrives. These are two
reasons to describe the system as an acceleration sensor.
Despite these acceleration events, I have described my sensor as a
velocity device. I do this because maximum output of the sensor occurs
when the pendulum is moving at maximum velocity. Or at least that is
what I believe is happening.
I think of my pendulum as being set in motion by my direct coupled
damper, direct coupled sensor, supporting spring, hinge, and surrounding
air. The sequence of events is: (1)earth moves; (2)damper, sensor,
spring, hinge and air move; (3)pendulum responds to forces of
acceleration from damper, sensor, spring, hinge, and air. Once moving,
the pendulum begins integrating all the instantaneous forces which will
increase at different rates, and will not stop relative to earth until
all the absorbed energy has been dissipated, which will not occur until
some time period after the earth motion has stopped. This time delay
is dramatic if one watches an in-car pendulum while stopping the car.
There seems to be some logic in classifying a sensor by when peak output
is reached relative to pendulum velocity as measured against earth. A
strain gage mounted on the side of a flexible pendulum arm should be a
pure acceleration measure. A magnetic system can be closely coupled an
be an acceleration system, or could be lightly coupled with very little
effect on the velocity of the pendulum. A capacity measuring position
indicator would have a negligible force couple to the pendulum but not a
zero force because a conductor or dielectric will be pulled into the
space between the fixed plates proportional to the applied voltage. With
negligible coupling, capacity sensors would be position indicators.
Direct coupled sensors appear to cover nearly the entire range between
sensing acceleration and sensing displacement.
Amateur seismology is certainly a good way to experiment and learn
physics. Thanks to you and several other very knowledgeable people for
making this hobby very worthwhile and enjoyable.
Best wishes,
Roger
psn-l-digest-request@.............. wrote:
..------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
| Message 1 |
'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
Subject: Re: Digest from 01/21/2007 00:00:40
From: Randall Peters
Date: Mon, 22 Jan 2007 09:47:19 -0500
This is a multi-part message in MIME format.
--Boundary_(ID_VPjS9T5orF39c2uYkK0SQA)
Content-type: text/plain; charset=iso-8859-1
Content-transfer-encoding: 8BIT
Roger, I have respnded to your request for help; i.e.,
"This brings up a very important point--what is the pendulum sensor
reading? Is it acceleration, velocity, or displacement? I need help here. "
With all the confusion as to how a seismometer functions, one has to wonder if Einstein was
the only one who ever acquired a complete conceptual
mastery of inertia. His principle of relativity states that the ``laws of physics remain the
same for any non-accelerating frame of reference''. In
practical terms, this equivalence of inertial reference frames means that it is impossible
to detect uniform motion on the basis of measurements
conducted inside a box, such as a seismometer. Thus the only feature of motion having any
importance whatsoever to a seismometer is acceleration
of the case that supports its inertial mass M. It is very common to erroneously believe that
any type motion of the case will be met with displacement
of M relative to the case, because of the inertia of M. Be sure to understand that the only
property of the motion that is ``resisted'' by M is the
acceleration. Thus the acceleration is the only thing that can be directly measured!!
Velocity and position, the other kinematic variables so frequently
discussed in seismology, can only be inferred from the acceleration measurement. Unlike the
quintessential acceleration, they cannot be directly
measured, even though they are frequently specified.
The output from a seismometer is directly proportional to acceleration, as long as the
acceleration takes place at a frequency
lower than the natural (eigen) frequency of the instrument, and additionally, it is
operating with damping that is near critical. When the frequency of
the drive is higher than the natural frequency of the instrument, the response of the
instrument is attenuated by the ratio of the square of the drive
frequency to the square of the eigenfrequency. If one is talking about the ground
displacement, as opposed to the acceleration, just the opposite
behavior is found. For those who want to believe that a seismometer responds directly to
ground displacement, complete confusion results.
It is also important to note that the horizontal seismometer, such as a pendulum,
responds to more than one type of acceleration. From ``inside the
box'' of the instrument there is no way to distinguish between these two forms of
acceleration, which are (i) horizontal acceleration of the instrument,
and (ii) changes in orientation of the box (tilt) relative to the direction of the local
field of the earth g of the earth, having the magnitude of 9.8 m/s2.
Randall
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Updated version of "Interpreting Seismograms"
From: "Thomas Dick" dickthomas01@.............
Date: Tue, 23 Jan 2007 10:04:47 -0600
This is a very fine website -- thanks for bringing it to my attention!
This is a very fine website -- thanks =
for bringing=20
it to my attention!
Subject: Sensor Type
From: Roger Sparks rsparks@..........
Date: Tue, 23 Jan 2007 08:19:45 -0800
Good Morning All,
Yesterday I posted a message on this subject that included the statement :
"There seems to be some logic in classifying a sensor by when peak output
is reached relative to pendulum velocity as measured against earth. A
strain gage mounted on the side of a flexible pendulum arm should be a
pure acceleration measure."
Night time is great for thinking and I realized that with this sensor,
maximum acceleration would occur at the same time as maximum
displacement. The sensor output could be correctly labeled either
"displacement" or "acceleration". Both terms would be correct so the
choice of label would depend upon which physical property you were
trying to use or emphasize.
Roger
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Earthquake in North sea
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 23 Jan 2007 18:29:18 +0000
Hi all
Today at 17:32 there was a ML4.1 earthquake in North sea. The location
is unusual. More detail here,
http://www.emsc-csem.org/index.php?page=current&sub=detail&id=38745
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Sensor Type (was Pendulum Q)
From: ChrisAtUpw@.......
Date: Tue, 23 Jan 2007 19:23:56 EST
In a message dated 23/01/2007, rsparks@.......... writes:
Randle, Thanks for the thought provoking response.
I can understand what you are saying about direct coupled sensing of
pendulums, but I think I am correct in saying that your comments are limited to
sensors that actually extract some power from the pendulum motion. A sensing
system that (for instance) that counted area sweeping past a camera in a time
period should not count as a direct coupled sensor.
Hi Roger,
It should apply to any sensor, but if it exchanges energy there will be
a perturbation.
If it senses displacement you will sense position.
If it is a velocity sensor you will sense velocity.
If it is a force sensor you will sense acceleration.
I am using a magnetic/coil sensing system with a heavy damper. The system is
near or even more than critically damped. My sensing magnet and coil are
not providing much load on the pendulum, most of the energy captured by the
pendulum is dissipated in the damper. I certainly agree that my sensing system
is really acceleration based as it does load and reduce the pendulum speed.
The sensor also acts to accelerate the pendulum from a standing start when a
wave arrives. These are two reasons to describe the system as an acceleration
sensor.
Despite these acceleration events, I have described my sensor as a velocity
device. I do this because maximum output of the sensor occurs when the
pendulum is moving at maximum velocity. Or at least that is what I believe is
happening.
It IS a velocity sensor in this case. For short periods, the mass is
'stationary' and the relative linear motion = the earth motion. You have an
inductive / magnetic sensor, which responds to the differential of the field
value = velocity. If instead you had an LVDT position sensor, you would read
linear distance = quake amplitude for the same signal, but at a different time.
I think of my pendulum as being set in motion by my direct coupled
damper, direct coupled sensor, supporting spring, hinge, and surrounding
air. The sequence of events is: (1)earth moves; (2)damper, sensor,
spring, hinge and air move; (3)pendulum responds to forces of
acceleration from damper, sensor, spring, hinge, and air. Once moving,
the pendulum begins integrating all the instantaneous forces which will
increase at different rates, and will not stop relative to earth until
all the absorbed energy has been dissipated, which will not occur until
some time period after the earth motion has stopped. This time delay
is dramatic if one watches an in-car pendulum while stopping the car.
There seems to be some logic in classifying a sensor by when peak output
is reached relative to pendulum velocity as measured against earth. A
strain gage mounted on the side of a flexible pendulum arm should be a
pure acceleration measure. A magnetic system can be closely coupled an
be an acceleration system, or could be lightly coupled with very little
effect on the velocity of the pendulum. A capacity measuring position
indicator would have a negligible force couple to the pendulum but not a
zero force because a conductor or dielectric will be pulled into the
space between the fixed plates proportional to the applied voltage.
Depends on the type of capacity detector. The forces are usually small
compared to mg.
With negligible coupling, capacity sensors would be position indicators.
Direct coupled sensors appear to cover nearly the entire range between
sensing acceleration and sensing displacement.
They don't have to, but all the capacity detectors that I know of sense
position.
Subject: Re: Digest from 01/21/2007 00:00:40
From: Randall Peters
Date: Mon, 22 Jan 2007 09:47:19 -0500
Roger, I have respnded to your request for help; i.e.,
"This brings up a very important point - what is the pendulum sensor
reading? Is it acceleration, velocity, or displacement? I need help here.
In practical terms, this equivalence of inertial reference frames means that
it is impossible to detect uniform motion on the basis of measurements
conducted inside a box, such as a seismometer. Thus the only feature of motion
having any
importance whatsoever to a seismometer is acceleration of the case that
supports its inertial mass M. It is very common to erroneously believe that any
type motion of the case will be met with displacement of M relative to the
case, because of the inertia of M.
I am trying to think of an occasion when this is not true? If the
inertia is large compared to any force, the mass will be 'stationary' / moving with
a fixed relative velocity.
Be sure to understand that the only property of the motion that is
``resisted'' by M is the acceleration. Thus the acceleration is the only thing that
can be directly measured!!
OK
Velocity and position, the other kinematic variables so frequently discussed
in seismology, can only be inferred from the acceleration measurement.
Unlike the
quintessential acceleration, they cannot be directly measured, even though
they are frequently specified.
OK
The output from a seismometer is directly proportional to acceleration, as
long as the acceleration takes place at a frequency lower than the natural
(eigen) frequency of the instrument, and additionally, it is operating with
damping that is near critical.
--> Very long period signals > resonant period
When the frequency of the drive is higher than the natural frequency of the
instrument, the response of the instrument is attenuated by the ratio of the
square of the drive frequency to the square of the eigenfrequency. If one is
talking about the ground displacement, as opposed to the acceleration, just
the opposite
behavior is found.
--> NORMAL operation < resonant period.
For those who want to believe that a seismometer responds directly to
ground displacement, complete confusion results.
--> Not for this bunny.
It is also important to note that the horizontal seismometer, such as a
pendulum,
responds to more than one type of acceleration. From ``inside the box'' of
the instrument there is no way to distinguish between these two forms of
acceleration, which are (i) horizontal acceleration of the instrument, and (ii)
changes in orientation of the box (tilt) relative to the direction of the local
field of the earth g of the earth, having the magnitude of 9.8 m/s2.
--> It can get confusing when you ALSO rotate the seismometer case, like in
a real quake, rather than just moving it laterally.
Regards,
Chris Chapman
In a message dated 23/01/2007, rsparks@.......... writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20
size=3D2>Randle, Thanks for the thought provoking response. I=20
can understand what you are saying about direct coupled sensing of pendulu=
ms,=20
but I think I am correct in saying that your comments are limited to senso=
rs=20
that actually extract some power from the pendulum motion. A sensing=
=20
system that (for instance) that counted area sweeping past a camera in a t=
ime=20
period should not count as a direct coupled sensor.
Hi Roger,
It should apply to any sensor, but if it exchan=
ges=20
energy there will be a perturbation.
If it senses displacement you will sense=20
position.
If it is a velocity sensor you will sense=20
velocity.
If it is a force sensor you will sense=20
acceleration.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>I am=20
using a magnetic/coil sensing system with a heavy damper. The system=20=
is=20
near or even more than critically damped. My sensing magnet and coil=20=
are=20
not providing much load on the pendulum, most of the energy captured by th=
e=20
pendulum is dissipated in the damper. I certainly agree that my sensing sy=
stem=20
is really acceleration based as it does load and reduce the pendulum=20
speed. The sensor also acts to accelerate the pendulum from a standin=
g=20
start when a wave arrives. These are two reasons to describe the syst=
em=20
as an acceleration sensor.
Despite these acceleration events=
, I=20
have described my sensor as a velocity device. I do this because maximum=20
output of the sensor occurs when the pendulum is moving at maximum=20
velocity. Or at least that is what I believe is happening.=20
It IS a velocity sensor in this case. For short=
=20
periods, the mass is 'stationary' and the relative linear motion =3D th=
e=20
earth motion. You have an inductive / magnetic sensor, which responds=20=
to=20
the differential of the field value =3D velocity. If instead you had an LVDT=
=20
position sensor, you would read linear distance =3D quake amplitude for the=20=
same=20
signal, but at a different time.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>I think=20
of my pendulum as being set in motion by my direct coupled damper, dir=
ect=20
coupled sensor, supporting spring, hinge, and surrounding air. &n=
bsp;=20
The sequence of events is: (1)earth moves; (2)damper, sensor, spring,=20
hinge and air move; (3)pendulum responds to forces of acceleration fro=
m=20
damper, sensor, spring, hinge, and air. Once moving, the=20
pendulum begins integrating all the instantaneous forces which will=20
increase at different rates, and will not stop relative to earth until=
=20
all the absorbed energy has been dissipated, which will not occur unti=
l=20
some time period after the earth motion has stopped. This=20=
time=20
delay is dramatic if one watches an in-car pendulum while stopping the=
=20
car.
There seems to be some logic in classifying a sensor by when p=
eak=20
output is reached relative to pendulum velocity as measured against=20
earth. A strain gage mounted on the side of a flexible=20
pendulum arm should be a pure acceleration measure. A magn=
etic=20
system can be closely coupled an be an acceleration system, or could b=
e=20
lightly coupled with very little effect on the velocity of the=20
pendulum. A capacity measuring position indicator would ha=
ve a=20
negligible force couple to the pendulum but not a zero force because a=
=20
conductor or dielectric will be pulled into the space between the fixe=
d=20
plates proportional to the applied voltage.
Depends on the type of capacity detector. The=20
forces are usually small compared to mg.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>With=20
negligible coupling, capacity sensors would be position=20
indicators. Direct coupled sensors appear to cover nearly=20=
the=20
entire range between sensing acceleration and sensing=20
displacement.
They don't have to, but all the capacity detect=
ors=20
that I know of sense position.
Roger, I have respnded to your request for help;=20
i.e., "This brings up a very important point - what is the pendulum=20
sensor reading? Is it acceleration, velocity, or=20
displacement? I need help here.
In practical terms=
,=20
this equivalence of inertial reference frames means that it is impossible=20=
to=20
detect uniform motion on the basis of measurements conducted inside a box,=
=20
such as a seismometer. Thus the only feature of motion having=20
any importance whatsoever to a seismometer is acceleration of the case=20=
that=20
supports its inertial mass M. It is very common to erroneously believe tha=
t=20
any type motion of the case will be met with displacement of M relative to=
the=20
case, because of the inertia of M.
I am trying to think of an occasion when this i=
s=20
not true? If the inertia is large compared to any force, the mass will be=20
'stationary' / moving with a fixed relative velocity.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Be sure=20
to understand that the only property of the motion that is ``resisted'' by=
M=20
is the acceleration. Thus the acceleration is the only thing that can be=20
directly measured!!
OK
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Velocity=20
and position, the other kinematic variables so frequently discussed in=20
seismology, can only be inferred from the acceleration measurement. Unlike=
=20
the quintessential acceleration, they cannot be directly measured, even=
=20
though they are frequently specified.
OK
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20
size=3D2> The output from a seismometer is directly=20
proportional to acceleration, as long as the acceleration takes place at a=
=20
frequency lower than the natural (eigen) frequency of the instrument, and=20
additionally, it is operating with damping that is near critical.=20
--> Very long period signals > resonant period
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>When the=20
frequency of the drive is higher than the natural frequency of the instrum=
ent,=20
the response of the instrument is attenuated by the ratio of the square of=
the=20
drive frequency to the square of the eigenfrequency. If one is talking abo=
ut=20
the ground displacement, as opposed to the acceleration, just the=20
opposite behavior is found.
--> NORMAL operation < resonant period.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>For=20
those who want to believe that a seismometer responds directly to groun=
d=20
displacement, complete confusion results.
--> Not for this bunny.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20
size=3D2> It is also important to note that the horizont=
al=20
seismometer, such as a pendulum, responds to more than one type of=20
acceleration. From ``inside the box'' of the instrument there is no way to=
=20
distinguish between these two forms of acceleration, which are (i) horizon=
tal=20
acceleration of the instrument, and (ii) changes in orientation of the box=
=20
(tilt) relative to the direction of the local field of the earth g of the=20
earth, having the magnitude of 9.8 m/s2.
--> It can get confusing when you ALSO rotate the seismometer case,=20=
like=20
in a real quake, rather than just moving it laterally.
Regards,
Chris Chapman
Subject: Re: Pendulum Q
From: Brett Nordgren Brett3mr@.............
Date: Tue, 23 Jan 2007 19:31:51 -0500
Dr. Peters,
I quite agree that uniform motion of an inertial frame of reference is not
observable within it; for example the fact that we're moving at roughly 2 x
10^20 nanometers per second around the sun should not interfere with our
ability to make sensitive seismic measurements.
However, I am a bit confused about your comments on measuring ground
motion. I'd like to see if a thought-experiment approach might help me
understand. Let me borrow Einstein's thought-experiment box, the one with
no windows that is big enough to let me get inside. Sitting in the box, I
coat the bottom with thought-experiment ice, the kind that has no
friction. Then I set a 1Kg brass weight on the ice in the center of the
floor and wait for the thought-experiment earthquake to occur, which
happens right on time. Being that the quake is conveniently close, I
observe that the mass appears to be moving, which I record with my video
camera. The question is, what am I observing when I plot the motion of the
weight? And then, can I tell anything about the nature of the motion of
the box (i.e. ground velocity or acceleration) from analyzing the weight's
apparent motion inside the box? Also, I observe that , since there can be
no (horizontal) force acting on the weight because of the ice, it will be
seeing no (horizontal) acceleration at all.
Brett
At 09:47 AM 1/22/2007 -0500, you wrote:
>Roger, I have respnded to your request for help; i.e.,
>"This brings up a very important point--what is the pendulum sensor
>reading? Is it acceleration, velocity, or displacement? I need help here. "
>
>With all the confusion as to how a seismometer functions, one has to
>wonder if Einstein was
>the only one who ever acquired a complete conceptual
>mastery of inertia. His principle of relativity states that the ``laws of
>physics remain the
>same for any non-accelerating frame of reference''. In
>practical terms, this equivalence of inertial reference frames means that
>it is impossible
>to detect uniform motion on the basis of measurements
>conducted inside a box, such as a seismometer. Thus the only feature of
>motion having any
>importance whatsoever to a seismometer is acceleration
>of the case that supports its inertial mass M. It is very common to
>erroneously believe that
>any type motion of the case will be met with displacement
>of M relative to the case, because of the inertia of M. Be sure to
>understand that the only
>property of the motion that is ``resisted'' by M is the
>acceleration. Thus the acceleration is the only thing that can be directly
>measured!!
>Velocity and position, the other kinematic variables so frequently
>discussed in seismology, can only be inferred from the acceleration
>measurement. Unlike the
>quintessential acceleration, they cannot be directly
>measured, even though they are frequently specified.
> The output from a seismometer is directly proportional to
> acceleration, as long as the
>acceleration takes place at a frequency
>lower than the natural (eigen) frequency of the instrument, and
>additionally, it is
>operating with damping that is near critical. When the frequency of
>the drive is higher than the natural frequency of the instrument, the
>response of the
>instrument is attenuated by the ratio of the square of the drive
>frequency to the square of the eigenfrequency. If one is talking about the
>ground
>displacement, as opposed to the acceleration, just the opposite
>behavior is found. For those who want to believe that a seismometer
>responds directly to
>ground displacement, complete confusion results.
> It is also important to note that the horizontal seismometer, such as
> a pendulum,
>responds to more than one type of acceleration. From ``inside the
>box'' of the instrument there is no way to distinguish between these two
>forms of
>acceleration, which are (i) horizontal acceleration of the instrument,
>and (ii) changes in orientation of the box (tilt) relative to the
>direction of the local
>field of the earth g of the earth, having the magnitude of 9.8 m/s2.
> Randall
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Pendulum Q
From: ChrisAtUpw@.......
Date: Wed, 24 Jan 2007 20:33:55 EST
In a message dated 24/01/2007, Brett3mr@............. writes:
Let me borrow Einstein's thought-experiment box, the one with
no windows that is big enough to let me get inside. Sitting in the box, I
coat the bottom with thought-experiment ice, the kind that has no
friction. Then I set a 1Kg brass weight on the ice in the center of the
floor and wait for the thought-experiment earthquake to occur, which
happens right on time. Being that the quake is conveniently close, I
observe that the mass appears to be moving, which I record with my video
camera. The question is, what am I observing when I plot the motion of the
weight? And then, can I tell anything about the nature of the motion of
the box (i.e. ground velocity or acceleration) from analyzing the weight's
apparent motion inside the box? Also, I observe that, since there can be
no (horizontal) force acting on the weight because of the ice, it will be
seeing no (horizontal) acceleration at all.
Hi Brett,
You are recording both the position and the time of relative movements
of the mass. From this you can infer the lateral acceleration and velocity of
the frame of reference, if you know that the mass is not being accelerated.
Regards,
Chris Chapman
In a message dated 24/01/2007, Brett3mr@............. writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Let me=20
borrow Einstein's thought-experiment box, the one with no windows that=
is=20
big enough to let me get inside. Sitting in the box, I coat the=20
bottom with thought-experiment ice, the kind that has no friction. The=
n I=20
set a 1Kg brass weight on the ice in the center of the floor and wait=20=
for=20
the thought-experiment earthquake to occur, which happens right on=20
time. Being that the quake is conveniently close, I observe that=20=
the=20
mass appears to be moving, which I record with my video camera. The=20
question is, what am I observing when I plot the motion of the=20
weight? And then, can I tell anything about the nature of the mot=
ion=20
of the box (i.e. ground velocity or acceleration) from analyzing the=20
weight's apparent motion inside the box? Also, I observe that, si=
nce=20
there can be no (horizontal) force acting on the weight because of the=
=20
ice, it will be seeing no (horizontal) acceleration at=20
all.
Hi Brett,
You are recording both the position and the tim=
e of=20
relative movements of the mass. From this you can infer the lateral accelera=
tion=20
and velocity of the frame of reference, if you know that the mass is no=
t=20
being accelerated.
Regards,
Chris Chapman
Subject: Re: Pendulum Q
From: Brett Nordgren Brett3mr@.............
Date: Wed, 24 Jan 2007 21:22:44 -0500
>Hi Brett,
>
> You are recording both the position and the time of relative
> movements of the mass. From this you can infer the lateral acceleration
> and velocity of the frame of reference, if you know that the mass is not
> being accelerated.
>
> Regards,
>
> Chris Chapman
Chris,
Thanks for your comment, that's exactly what I was trying to demonstrate.
On the one hand, there is the derivative relationship between ground
displacement, velocity and acceleration and on the other, the practical
problem of constructing a device to measure them. My 'experiment' was an
attempt to untangle the two issues.
Regards,
Brett
Hi Brett,
You are recording both the position and the time of
relative movements of the mass. From this you can infer the lateral
acceleration and velocity of the frame of reference, if you know that the
mass is not being accelerated.
Regards,
Chris Chapman
Chris,
Thanks for your comment, that's exactly what I was trying to
demonstrate.
On the one hand, there is the derivative relationship between ground
displacement, velocity and acceleration and on the other, the practical
problem of constructing a device to measure them. My 'experiment'
was an attempt to untangle the two issues.
Regards,
Brett
Subject: what is measured by seismometers
From: Randall Peters PETERS_RD@..........
Date: Thu, 25 Jan 2007 09:11:32 -0500
Every seismometer responds to acceleration of the earth; meaning the mass moves
relative to the case because the case is accelerated. In thinking about Newton's
2nd law, you can see that it is only an acceleration that "starts" anything of
dynamics type. Although we develop kinematics by taking the derivative of position
to get velocity and the derivative of velocity to get acceleration; this approach
can easily confuse one into getting the 'cart before the horse'. State variables
of nature (name used by dynamicists for position, velocity, and acceleration)
evolve only in one direction -- just opposite to our first exposure to calculus --
acceleration is the fundamental kinematic variable. The position (deflection) of
the mass is directly proportional to the acceleration for a critically damped
instrumentas long as the rate of change of the acceleration (specified in terms of
frequency) is less than the natural frequency of the instrument. Even if the
frequency of the drive is greater than the natural frequency, it is still a
straightforward matter to correct for the attenuation. Thus the mass movement of
every seismometer directly measures only one thing--acceleration. Of course the
movement of the seismic mass can be used to describe the earth's velocity by
integrating the output of a sensor that measures mass position (since the mass
deflection is directly proportional to acceleration, at least for drive frequencies
lower than the eigenfrequency).
Before I say anything further about this, let me point out that it is a reasonable
assumption that whatever decent linear sensor we use (one not worthless because
of friction), it has no significant influence on the evolution of the state
variables as long as we are not using force feedback that involves an actuator. Of
course most of the commercial instruments use force-balance with an actuator, so
the arguments that follow must be modified to describe them.
The most common older instrument is not measuring the mass position; rather by
means of a Faraday's law detector (time changing magnetic flux; i.e., magnet/coil)
it is measuring the time rate of change of position. Since the position is
determined by the acceleration--simply stated, such a sensor measures the
derivative of the ground's acceleration, which is called the 'jerk'. For harmonic
motions of the ground (sine or cosine), the velocity of the ground motion is given
by omega times the displacement of the ground (same as derivative of position to
get velocity), where omega is two-pi times the frequency. Similarly the
acceleration is equal to omega times the velocity. Thus there is a simple
connection between the amplitude of the mass displacement Am and the ground
amplitude A for drive frequency below natural frequency. It is Am = omega squared
times A divided by omega0 squared, where both A and Am are in meters. Omega0 is
two pi times the natural frequency of the instrument. For a jerk detector the
relationship between Am and the ground velocity amplitude V in meters per second is
given by omega times V divided by omega0 squared. One can get a better feel for
all of this by looking at instrument transfer functions; the best graphics that I
know about are provided on John Lahrs website at
http://jclahr.com/science/psn/response/plots.jpg
Of these six cases, the upper right graph is the fundamental one. It applies to
the output from our VolksMeter; labeled lctst in the data on Larry Cochranes
webpages. The lower right graph is what gets output from the VolksMeter after
integration; labeled lctst1 on Larrys pages.
There is a subtlety in the use of these graphs to describe the old-style jerk
sensor (and for that matter the broadband units, since their output is similar,
except they use force-balance by means of an actuator to lower omega0). Although
the expression velocity sensing is used to describe such an output, bear in mind
what I said above. It measures the velocity of the seismic mass motion, not the
velocity of the ground. Since the mass motion is proportional to the acceleration
of the ground, what the instrument is measuring is the jerk of the ground (third
derivative of the displacement of the ground). On the basis of the harmonic drive
assumption, this third derivative can be related to the first derivative, which is
the time rate of change (velocity) of the displacement of the ground. In other
words, for a monochromatic harmonic drive (and a Hookes law mechanical oscillator
if one were to exist), the lower middle graph is a valid representation of how such
a sensors output voltage responds to ground velocity. When the frequency of the
drive is changing, this is no longer as good a sensor to describe what the earth is
doing as compared to a position sensor. Not only is there a loss of information
with the velocity sensor (its inability to see offsets, which get removed except
for transients because of the derivative); there are also even some false data
consequences. Let me give you a brief explanation of the artifacts that can be
introduced.
The potential energy function of a seismometer is not a parabola, the so-called
harmonic oscillator potential. Hookes law does not apply to real systems because
of defect structures. At low energies (the place now begging for better data) the
parabola is modulated with fine structure; i.e., the potential is ragged rather
than smooth. When a seismometer with this fine structure is driven by an
acceleration of the earth, the simple connection between ground velocity and
Faraday-law sensor output voltage is no longer trivial. The nonlinear nature of
the dynamics gives rise to a host of complications. Deconvolution is no longer
possible because superposition (the standard approach for solving linear equations
of motion) is no longer valid.
Having spent much of my career studying these nonlinearities, I am probably the
only person with connections to seismology, who is intimately familiar with the
challenges through direct experience. I intend to generate some simulations of
representative cases (ones relevant to free earth oscillations) to illustrate some
of the pathologies associated with velocity sensing. The artifacts generated
by a non-ideal (nonlinear) oscillator are worse for a velocity sensor than for a
position sensor. Not only that, the noise equivalent power spectral density is
also worse at low frequencies. Thus the velocity sensor introduces more in the way
of artifacts having frequencies above the signal of interest, while at the same
time having a poorer signal to noise ratio when it comes to the actual frequency of
interest.
Randall
psn-l-digest-request@.............. wrote:
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 1 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Pendulum Q
> From: ChrisAtUpw@.......
> Date: Wed, 24 Jan 2007 20:33:55 EST
>
> -------------------------------1169688835
> Content-Type: text/plain; charset="US-ASCII"
> Content-Transfer-Encoding: 7bit
>
>
> In a message dated 24/01/2007, Brett3mr@............. writes:
>
> Let me borrow Einstein's thought-experiment box, the one with
> no windows that is big enough to let me get inside. Sitting in the box, I
> coat the bottom with thought-experiment ice, the kind that has no
> friction. Then I set a 1Kg brass weight on the ice in the center of the
> floor and wait for the thought-experiment earthquake to occur, which
> happens right on time. Being that the quake is conveniently close, I
> observe that the mass appears to be moving, which I record with my video
> camera. The question is, what am I observing when I plot the motion of the
> weight? And then, can I tell anything about the nature of the motion of
> the box (i.e. ground velocity or acceleration) from analyzing the weight's
> apparent motion inside the box? Also, I observe that, since there can be
> no (horizontal) force acting on the weight because of the ice, it will be
> seeing no (horizontal) acceleration at all.
>
> Hi Brett,
>
> You are recording both the position and the time of relative movements
> of the mass. From this you can infer the lateral acceleration and velocity of
> the frame of reference, if you know that the mass is not being accelerated.
>
> Regards,
>
> Chris Chapman
>
> -------------------------------1169688835
> Content-Type: text/html; charset="US-ASCII"
> Content-Transfer-Encoding: quoted-printable
>
>
>
>
>
> Arial"=20
> bottomMargin=3D7 leftMargin=3D7 topMargin=3D7 rightMargin=3D7> e_document=20
> face=3DArial color=3D#000000 size=3D2>
>
>
In a message dated 24/01/2007, Brett3mr@............. writes:
> style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><=
> FONT=20
> style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
> =3D2>Let me=20
> borrow Einstein's thought-experiment box, the one with no windows that=
> is=20
> big enough to let me get inside. Sitting in the box, I coat the=20
> bottom with thought-experiment ice, the kind that has no friction. The=
> n I=20
> set a 1Kg brass weight on the ice in the center of the floor and wait=20=
> for=20
> the thought-experiment earthquake to occur, which happens right on=20
> time. Being that the quake is conveniently close, I observe that=20=
> the=20
> mass appears to be moving, which I record with my video camera. The=20
> question is, what am I observing when I plot the motion of the=20
> weight? And then, can I tell anything about the nature of the mot=
> ion=20
> of the box (i.e. ground velocity or acceleration) from analyzing the=20
> weight's apparent motion inside the box? Also, I observe that, si=
> nce=20
> there can be no (horizontal) force acting on the weight because of the=
> =20
> ice, it will be seeing no (horizontal) acceleration at=20
> all.
>
>
Hi Brett,
>
>
You are recording both the position and the tim=
> e of=20
> relative movements of the mass. From this you can infer the lateral accelera=
> tion=20
> and velocity of the frame of reference, if you know that the mass is no=
> t=20
> being accelerated.
>
>
Regards,
>
>
Chris Chapman
>
> -------------------------------1169688835--
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 2 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: Pendulum Q
> From: Brett Nordgren
> Date: Wed, 24 Jan 2007 21:22:44 -0500
>
> --=====================_49664656==_.ALT
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> >Hi Brett,
> >
> > You are recording both the position and the time of relative
> > movements of the mass. From this you can infer the lateral acceleration
> > and velocity of the frame of reference, if you know that the mass is not
> > being accelerated.
> >
> > Regards,
> >
> > Chris Chapman
>
> Chris,
>
> Thanks for your comment, that's exactly what I was trying to demonstrate.
>
> On the one hand, there is the derivative relationship between ground
> displacement, velocity and acceleration and on the other, the practical
> problem of constructing a device to measure them. My 'experiment' was an
> attempt to untangle the two issues.
>
> Regards,
> Brett
> --=====================_49664656==_.ALT
> Content-Type: text/html; charset="us-ascii"
>
>
>
Hi Brett,
>
> You are recording both the position and the time of
> relative movements of the mass. From this you can infer the lateral
> acceleration and velocity of the frame of reference, if you know that the
> mass is not being accelerated.
>
> Regards,
>
> Chris Chapman
> Chris,
> Thanks for your comment, that's exactly what I was trying to
> demonstrate.
> On the one hand, there is the derivative relationship between ground
> displacement, velocity and acceleration and on the other, the practical
> problem of constructing a device to measure them. My 'experiment'
> was an attempt to untangle the two issues.
> Regards,
> Brett
>
> --=====================_49664656==_.ALT--
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-DIGEST-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
Subject: Earthquake or a noise ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 27 Jan 2007 05:34:59 +0000
Hi all
Yesterday at 11:40 UTC I did record a strange signal. It looks like a
earthquake, but a really small one. But I am not sure, this might just
be a noise. But I want to get others opinion on this signal.
The files can be downloaded from here,
http://157.157.215.56/~jonfr/earthquake/
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Clock drift ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 27 Jan 2007 12:32:13 +0000
Hi all
I think my system did suffer from a GPS connection loss for some unkown
reasons. This appears to have resaulted in a rater annoying clockdrift.
Or at least I think so. Clear examples are in my latest traces. I didn't
notice this, because WinSDR did show (L) as normal. But normally, when
the GPS clock drops out, it shows (N). The computer clock is in check
with NTP program that I am running, so drift in the computer clock is
minimal.
A earthquake that is 82 km away from me.
http://seismicnet.com/cgi-dos/makegif.exe?/quakes/0701/070126.061700.hvt1z.psn
A earthquake that is 182 km away from me.
http://seismicnet.com/cgi-dos/makegif.exe?/quakes/0701/070125.003700.hvt1z.psn
Is this a resault of a clock drift or a wrong p and s model. I've would
like to know. I did reboot the PSN hardware and I think everything is
back to normal for now, it appears. At least the p and s wave are in
correct places now.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Earthquake or a noise ?
From: "Geoffrey" gmvoeth@...........
Date: Sat, 27 Jan 2007 09:56:26 -0700
very interesting noise.
It is like a local disturbance of some kind.
local to the location of the seismometer sensor.
looks a lot like a cat jumped off something high
into the local vicinity of the sensor
then in a series of jumps went away from the sensor.
I would say you have some kind artifact that is not
related to Earthquakes.
----- Original Message -----
From: "Jón Frímann"
To: "PSN-Postlist"
Sent: Friday, January 26, 2007 10:34 PM
Subject: Earthquake or a noise ?
> Hi all
>
> Yesterday at 11:40 UTC I did record a strange signal. It looks like a
> earthquake, but a really small one. But I am not sure, this might just
> be a noise. But I want to get others opinion on this signal.
>
> The files can be downloaded from here,
> http://157.157.215.56/~jonfr/earthquake/
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Clock drift ?
From: "Geoffrey" gmvoeth@...........
Date: Sat, 27 Jan 2007 10:00:13 -0700
With any robot clock you must maintain
synchronization as often as possible and
your quartz crystal should be both calibrated
and oven controlled at some temp greater or lower
then will ever be experienced
at its location.
Most military oscillators are oven controlled
about 140deg fahrenheit which keeps it above
the hottest days.
----- Original Message -----
From: "Jón Frímann"
To: "PSN-Postlist"
Sent: Saturday, January 27, 2007 5:32 AM
Subject: Clock drift ?
> Hi all
>
> I think my system did suffer from a GPS connection loss for some unkown
> reasons. This appears to have resaulted in a rater annoying clockdrift.
> Or at least I think so. Clear examples are in my latest traces. I didn't
> notice this, because WinSDR did show (L) as normal. But normally, when
> the GPS clock drops out, it shows (N). The computer clock is in check
> with NTP program that I am running, so drift in the computer clock is
> minimal.
>
> A earthquake that is 82 km away from me.
> http://seismicnet.com/cgi-dos/makegif.exe?/quakes/0701/070126.061700.hvt1z.psn
>
> A earthquake that is 182 km away from me.
> http://seismicnet.com/cgi-dos/makegif.exe?/quakes/0701/070125.003700.hvt1z.psn
>
> Is this a resault of a clock drift or a wrong p and s model. I've would
> like to know. I did reboot the PSN hardware and I think everything is
> back to normal for now, it appears. At least the p and s wave are in
> correct places now.
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Clock drift ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 27 Jan 2007 19:45:01 +0000
Hi all
Is there any way that I can correct this clock drift in the effected
traces ?
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Clock drift ?
From: "tchannel" tchannel@..............
Date: Sat, 27 Jan 2007 12:48:34 -0700
Hi Jon, Are you using Winquake? There you can under "Time Information" Ted
----- Original Message -----
From: "Jón Frímann"
To:
Sent: Saturday, January 27, 2007 12:45 PM
Subject: Re: Clock drift ?
> Hi all
>
> Is there any way that I can correct this clock drift in the effected
> traces ?
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Clock drift ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 27 Jan 2007 19:59:12 +0000
Hi Ted
Yes, I am using WinQuake. It appears that I need to add 10 seconds to
the plots. Then I get accurate location for the P and S wave. I have to
do that with all of this weeks earthquakes, about 19 of them.
Thanks and Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Clock drift ?
From: "tchannel" tchannel@..............
Date: Sat, 27 Jan 2007 13:28:07 -0700
Hi Jon, This helped me too when someone pointed out that Winquake had this
feature. I am using a old computer with no internet connection, so I must
keep an eye on the clock. It will lose about 10 secs a day. I do try to
keep it accurate but sometimes the trace shows evidence that the clock is
wrong. This Winquake feature is very nice. Ted
----- Original Message -----
From: "Jón Frímann"
To:
Sent: Saturday, January 27, 2007 12:59 PM
Subject: Re: Clock drift ?
> Hi Ted
>
> Yes, I am using WinQuake. It appears that I need to add 10 seconds to
> the plots. Then I get accurate location for the P and S wave. I have to
> do that with all of this weeks earthquakes, about 19 of them.
>
> Thanks and Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Earthquake or a noise ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 27 Jan 2007 23:58:35 +0000
Hi Geoffrey
I do belive that this is a earthquake. But I am not sure, since I don't
have good experience in finding P and S wave. This event, if earthquake,
is extremly small, maybe less the ML 1.0. But I can't properly tell if
that is correct or not.
I know it was not a cat, noise from people and other living things is
quite diffrent.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Earthquake or a noise ?
From: "Geoffrey" gmvoeth@...........
Date: Sat, 27 Jan 2007 23:17:34 -0700
Hello Mr.Jón Frímann;
Thanks for the correction it is just that
such traces I receive are related to
things very close to my geophone here
and that is why i said what i did.
I get dogs and cats and other animals
here that will occassionally cause such
traces.
I have never in my life seen an EQ
like your trace is showing.
----- Original Message -----
From: "Jón Frímann"
To:
Sent: Saturday, January 27, 2007 4:58 PM
Subject: Re: Earthquake or a noise ?
> Hi Geoffrey
>
> I do belive that this is a earthquake. But I am not sure, since I don't
> have good experience in finding P and S wave. This event, if earthquake,
> is extremly small, maybe less the ML 1.0. But I can't properly tell if
> that is correct or not.
>
> I know it was not a cat, noise from people and other living things is
> quite diffrent.
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Earthquake or a noise ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sun, 28 Jan 2007 06:39:06 +0000
Hi
This event is quite strange, the axis register the movement as this.
North-south goes up, east-west goes down, vertical goes up. Noise
normally doesn't have the sharp beginning as earthquakes does, also with
noise, there is usally always just one spike, not two like in
earthquake. But I still need some input on this, too see if this is a
earthquake or not, because noise can still fool me.
I maybe record one or two events like this over the year. Last time I
did record a small event located at ~15 km away from me. It was a 1.1ML
event, it didn't register on the IMO network. Like this one, if
earthquake.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Clock drift ?
From: Larry Cochrane lcochrane@..............
Date: Mon, 29 Jan 2007 01:57:57 -0800
Hi Jón,
It may not be a timing problem. Since your event file shows that the A/D board was
locked to GPS time, I ready don't think your timing could be off by around 10 seconds.
You need the following for WinQuake to place the P and S markers correctly. Correct
station timing and latitude and longitude information, and for the event information
you need the correct time of origin, latitude, longitude and depth. You also need the
correct P and S travel-time model. If any of these parameters are not correct
WinQuake can't place the markers at the right spot on the seismogram.
If you think you are having a timing problem do the following. Using another source
for accurate time, I use the USA radio stations WWV/WWVH, jump near the sensor at the
top of the minute. While your jump may be off by a second you should be able to see
if the event file timing is off by 10 seconds.
Regards,
Larry Cochrane
Webtronics
Jón Frímann wrote:
> Hi all
>
> I think my system did suffer from a GPS connection loss for some unkown
> reasons. This appears to have resaulted in a rater annoying clockdrift.
> Or at least I think so. Clear examples are in my latest traces. I didn't
> notice this, because WinSDR did show (L) as normal. But normally, when
> the GPS clock drops out, it shows (N). The computer clock is in check
> with NTP program that I am running, so drift in the computer clock is
> minimal.
>
> A earthquake that is 82 km away from me.
> http://seismicnet.com/cgi-dos/makegif.exe?/quakes/0701/070126.061700.hvt1z.psn
>
> A earthquake that is 182 km away from me.
> http://seismicnet.com/cgi-dos/makegif.exe?/quakes/0701/070125.003700.hvt1z.psn
>
> Is this a resault of a clock drift or a wrong p and s model. I've would
> like to know. I did reboot the PSN hardware and I think everything is
> back to normal for now, it appears. At least the p and s wave are in
> correct places now.
>
> Regards.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Network report within Winquake
From: "Thomas Dick" dickthomas01@.............
Date: Mon, 29 Jan 2007 16:50:17 -0600
I would appreciate you comments. For four years I have type data into =
events within Winquake. It has worked for me but it isn't what Larry's =
program expects when you try to upload files to his "current events". If =
I understand his program, I am supposed to go to one of the sites =
listed, connect to it and download the data which Winquake will plug =
into my events. Most of his working sites are for California. I get my =
global data from the USGS =
http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/quakes_all.php =
and data for central US from Memphis =
http://folkworm.ceri.memphis.edu/recenteqs/Quakes/quakes0.html. Usually =
the USGS site is current to within a half hour of a major event and the =
Memphis site is current after the midmorning local next day. Adding =
sites to Larry's list doesn't seem to be a copy-paste option. What have =
I missed?
I would appreciate you comments. For =
four years I=20
have type data into events within Winquake. It has worked for me but it =
isn't=20
what Larry's program expects when you try to upload files to his =
"current=20
events". If I understand his program, I am supposed to go to one of the =
sites=20
listed, connect to it and download the data which Winquake will plug =
into my=20
events. Most of his working sites are for California. I get my global =
data from=20
the USGS http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/quakes_all.p=
hp and=20
data for central US from Memphis h=
ttp://folkworm.ceri.memphis.edu/recenteqs/Quakes/quakes0.html.=20
Usually the USGS site is current to within a half hour of a =
major event and=20
the Memphis site is current after the midmorning local next day. Adding =
sites to=20
Larry's list doesn't seem to be a copy-paste option. What have I=20
missed?
Subject: Re: Clock drift ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 30 Jan 2007 00:02:08 +0000
Hi Larry
This was a timeing problem. After I did restart the software and the
hardware the timeing for the events that did follow was correct. The
current p and s wave travel time model appears to work for Iceland, I am
using P_b.jb and S_b.jb files. For some reason WinSDR program did belive
it was still getting data from the gps antenna, even if the data was
wrong or not there at all and did create this time error. I unfortunaly
lost the log file, since WinSDR overwrites the log file when restarted,
insted of just writeing into it with diffrent time stamp.
Iceland doesn't have any such time radio signal source. I also don't
have the nessary setup on my WinSDR boards to connect it. The next radio
time source I have is located in England and that signal only works at
night. The computer clock is kept in sync with a ntp program, so that is
problay not the reason why the timeing data was wrong.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Earthquake or a noise ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 30 Jan 2007 00:08:57 +0000
Hi all
I still want get a opinion on this so I know if this is a earthquake or
a noise of a unusual type.
Geoffrey
The area where I live doesn't have many earthquakes over the year
(Nearby 70 - 300 Km, depending on direction), maybe 5 to 10 earthquakes
if it is a busy year and that only happens like every 5 - 10 years or
so. Not even that often. If this is a earthquake, it is quite unusual
for me to see it at this close distance to my location. But that might
just be because I have just had this station such a short time here.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Earthquake or a noise ?
From: "Geoffrey" gmvoeth@...........
Date: Mon, 29 Jan 2007 18:01:12 -0700
Hello Mr. Frímann;
I was just going by the fact the groups of
signals in your data appear to have
both slow attacks and slow decay
that make me think they are caused by something
approaching and departing the sensor area.
Attack and Decay are terms used in music
to describe a tonal envelope.
Earthquakes that I see almost always have a
sharp attack being practically instantaneous.
There is only one place i get odd P waves from
that slowly raise out of the noise and that
seems to be signals from the Gulf of California
in Northern Mexico.
Regards;
geoff
----- Original Message -----
From: "Jón Frímann"
To:
Sent: Monday, January 29, 2007 5:08 PM
Subject: Re: Earthquake or a noise ?
> Hi all
>
> I still want get a opinion on this so I know if this is a earthquake or
> a noise of a unusual type.
>
> Geoffrey
>
> The area where I live doesn't have many earthquakes over the year
> (Nearby 70 - 300 Km, depending on direction), maybe 5 to 10 earthquakes
> if it is a busy year and that only happens like every 5 - 10 years or
> so. Not even that often. If this is a earthquake, it is quite unusual
> for me to see it at this close distance to my location. But that might
> just be because I have just had this station such a short time here.
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Earthquake or a noise ?
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 30 Jan 2007 03:51:08 +0000
Hi Geoffrey
Noise, that I have encunterd so far. Always has a slow start with one
spike. Mostly from cars and alikes. The footprints I see always have one
spike, if there are two spikes they are sepirated with a gap in them.
What baffels me with this how the Z appears, N-S and E-W appears to be
normal. Execpt that the location is really close to my geophone.
There are many old fault lines near me and many new faults lines close
to my locations, many of them are undocumented. But I am still wanting
more opintions on this. Your input on this Geoffrey is most welcomed.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Winquake question
From: "tchannel" tchannel@..............
Date: Tue, 30 Jan 2007 16:15:27 -0700
Hi Folks, I am using Winquake, works great, but I seem to have a =
problem. When I open a new event, the Display/Modify...Event =
information window is not blank....It appears to have numbers from =
earlier events. When I post new dates etc. I get a error "can't post P =
and S"
If I play with the "clear report information" button it clears =
everything but sometimes I have to do this two times. Once it is clear =
and the new info is entered it works fine and the P and S are posted.
In the past I thought this New Event information window was always =
blank. Could I have too many events?
Thanks, Ted
Hi Folks, I am using Winquake, =
works great,=20
but I seem to have a problem. When I open a new event, the=20
Display/Modify...Event information window is not blank....It appears to =
have=20
numbers from earlier events. When I post new dates etc. I =
get a=20
error "can't post P and S"
If I play with the "clear report =
information"=20
button it clears everything but sometimes I have to do this two times. =
Once it=20
is clear and the new info is entered it works fine and the P and S are=20
posted.
In the past I thought this New Event =
information=20
window was always blank. Could I have too many =
events?
Thanks, Ted
Subject: Nature cooperates
From: "Thomas Dick" dickthomas01@.............
Date: Thu, 1 Feb 2007 07:57:38 -0600
There was a State of Kentucky meeting in western Kentucky yesterday =
dedicated to earthquake awareness. Press, TV stations and many local =
officials attended. Two earthquakes (mag 2.9 & 2.7) occurred within a =
five hour period. Memphis shows no other earthquakes in Kentucky since =
August of last year. How's that for timing!
There was a State of Kentucky meeting =
in western=20
Kentucky yesterday dedicated to earthquake awareness. Press, TV stations =
and many local officials attended. Two earthquakes (mag 2.9 & =
2.7)=20
occurred within a five hour period. Memphis shows no other earthquakes =
in=20
Kentucky since August of last year. How's that for=20
timing!
Subject: Orientation of magnet with Lehman setup?
From: "Michael Kimzey" mckimzey@...........
Date: Thu, 01 Feb 2007 22:59:19 -0500
I have continued to modify my initial Lehman prototype. I had been getting
noise so I tried several things... 1) boom now made of aluminum, lead and
stainless steel. No iron present. 2) Magnet on ground and coil on boom.
3) Aluminum dampening.
These seem to have removed some noise but some still remained,
especially when little feet were jumping above the crawl space. Looking at
a design by Chris Chapman, he oriented the poles of the magnet up and down,
as opposed to sideways. I was wondering: is the up-down orientation better,
as any up-down motion of the ground (probably noise) would _not_ induce a
current because movement of the coil would then be parallel to the field
lines, while side-to-side movement (in the axis of the pendulum) would still
be perpendicular to the field lines and induce a current. Any thoughts?
A second question - some have reported that the SG has some limitation
because of electronics. With some other seismometer designs using
capacitance displacement (Allan Coleman's designs, volksmeter), has anyone
thought about changing the design of the SG to using capacitance
displacement, or would that be unfeasible?
- Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Orientation of magnet with Lehman setup?
From: ChrisAtUpw@.......
Date: Fri, 2 Feb 2007 11:05:03 EST
In a message dated 02/02/2007, mckimzey@........... writes:
I have continued to modify my initial Lehman prototype. I had been getting
noise so I tried several things... 1) boom now made of aluminum, lead and
stainless steel. No iron present. 2) Magnet on ground and coil on boom.
3) Aluminum dampening.
These seem to have removed some noise but some still remained,
especially when little feet were jumping above the crawl space. Looking at
a design by Chris Chapman, he oriented the poles of the magnet up and down,
as opposed to sideways. I was wondering: is the up-down orientation better,
as any up-down motion of the ground (probably noise) would _not_ induce a
current because movement of the coil would then be parallel to the field
lines, while side-to-side movement (in the axis of the pendulum) would still
be perpendicular to the field lines and induce a current. Any thoughts?
Hi Mike,
I have used both orientations. Can you check to see if up and down
motions of the mass produce any signal? Tap / thump the top of the frame? Some
seismometer constructions / suspensions are more rigid than others. If this is a
problem, it can be damped in two planes, using four square NdFeB magnets on
both backing plates with a vertical orientation.
You can also get problems if the centre of the damping force is at a
different height to the line joining the centre of mass to the bottom suspension
- eg rocking of the seismometer arm about it's long axis. I can't remember
your construction. Is there a photo anywhere? Twin wire V suspensions were
used on commercial instruments to avoid this.
The pounding of little (or big) feet is a real vibration.
I suggest that you view the background noise and type over 24 hr periods
to check for times of increased activity.
A second question - some have reported that the SG has some limitation
because of electronics. With some other seismometer designs using
capacitance displacement (Allan Coleman's designs, volksmeter), has anyone
thought about changing the design of the SG to using capacitance
displacement, or would that be unfeasible?
It should be relatively easy with Allan's circuit. You would probably
use a higher audio frequency to drive the sensor and phase sensitive detection.
The original SG circuit used two tuned resonant circuits and diode
rectification for the position sensor. Both are temperature sensitive and can cause
drifts, but a good thermally insulated case should minimise any problems.
Silicon diodes drift by ~2.5 mV / C Deg and you are interested in micro volt
resolution.
Regards,
Chris Chapman
In a message dated 02/02/2007, mckimzey@........... writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>I have=20
continued to modify my initial Lehman prototype. I had been getting=20
noise so I tried several things... 1) boom now made of aluminum, lead=20=
and=20
stainless steel. No iron present. 2) Magnet on ground and=20=
coil=20
on boom. 3) Aluminum dampening.
These=
=20
seem to have removed some noise but some still remained, especially wh=
en=20
little feet were jumping above the crawl space. Looking at a des=
ign=20
by Chris Chapman, he oriented the poles of the magnet up and down, as=20
opposed to sideways. I was wondering: is the up-down orientation bet=
ter,=20
as any up-down motion of the ground (probably noise) would _not_ induc=
e a=20
current because movement of the coil would then be parallel to the fie=
ld=20
lines, while side-to-side movement (in the axis of the pendulum) would=
=20
still be perpendicular to the field lines and induce a current. =20=
Any=20
thoughts?
Hi Mike,
I have used both orientations. Can you check to=
see=20
if up and down motions of the mass produce any signal? Tap / thump the top o=
f=20
the frame? Some seismometer constructions / suspensions are more rigid=20=
than=20
others. If this is a problem, it can be damped in two planes, using four squ=
are=20
NdFeB magnets on both backing plates with a vertical orientation.
You can also get problems if the centre of the=20
damping force is at a different height to the line joining the centre of mas=
s to=20
the bottom suspension - eg rocking of the seismometer arm about it's long ax=
is.=20
I can't remember your construction. Is there a photo anywhere? Twin wire V=20
suspensions were used on commercial instruments to avoid this.
The pounding of little (or big) feet is a real=20
vibration.
I suggest that you view the background noise an=
d=20
type over 24 hr periods to check for times of increased activity.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>A second=20
question - some have reported that the SG has some limitation because=20=
of=20
electronics. With some other seismometer designs using capacitanc=
e=20
displacement (Allan Coleman's designs, volksmeter), has anyone thought=
=20
about changing the design of the SG to using capacitance displacement,=
or=20
would that be unfeasible?
It should be relatively easy with Allan's circu=
it.=20
You would probably use a higher audio frequency to drive the sensor and phas=
e=20
sensitive detection. The original SG circuit used two tuned resonant circuit=
s=20
and diode rectification for the position sensor. Both are temperature sensit=
ive=20
and can cause drifts, but a good thermally insulated case should minimise an=
y=20
problems. Silicon diodes drift by ~2.5 mV / C Deg and you are interested in=20
micro volt resolution.
Regards,
Chris Chapman
Subject: WinSDR vs. AmaSys Software
From: "Jerry Payton" gpayton880@.......
Date: Fri, 2 Feb 2007 10:49:52 -0600
I was just curious (for experimental and comparison purposes) if AmaSys
software would ingest and display sensor signals via Larry Cochrane's
electronics package? Anybody ever tried?
Regards,
Jerry Payton
I was just curious (for experimental and comparison =
purposes) if=20
AmaSys software would ingest and display sensor signals via Larry =
Cochrane's=20
electronics package? Anybody ever tried?
Regards,
Jerry Payton
Subject: Re: Orientation of magnet with Lehman setup?
From: "Connie and Jim Lehman" lehmancj@...........
Date: Sat, 3 Feb 2007 15:53:08 -0500
----- Original Message -----
From: "Michael Kimzey"
To:
Sent: Thursday, February 01, 2007 10:59 PM
Subject: Orientation of magnet with Lehman setup?
MIKE --I read your note with interest. Seeing traces of "little feet"
above means your system is working. A long period horizontal system setup
in a home is often fraught with undesired traces due to normal activities of
people, appliances turning off & on, wind in and around the house blowing
trees or bushes within a few feet of the sensor, changes of temperature at
the sensor area--insects/spiders doing their thing walking the boom or using
it as an anchor. That shouldn't discourage one from running a system in a
remote ground level --home location .
You mention your design has the coil on the boom, and magnet on the
ground. That is quite ok I guess, but I have never understood the advantage
over the coil on the ground--with the coil on the ground, the boom is free
is any attachments.....Maybe I am missing something---
Of course the ideal location is an institutional building of some size,
at ground level in a small room/closet. The coil of course responds to 60
hz residual radiation around, and 40-50 hz mechanical noise from a nearby
mechanical HVAC room must be filtered out by a passive or active filter..
That is about as quiet as you can get short of a outdoor "bunker".
The trick is to minimize external noise wherever you are-- Chris
suggests checking the alignment of your damping with the boom axis--offset
could provide an unnecessary torque. I assume your damping ratio is ok--you
could change it a bit to see if that helps lessen the mechanical noise .
If your system is recording events as it should--regional and worldwide, you
will learn to live with the noise---no doubt the little feet above are happy
feet!!
Best wishes, Jim Lehman >
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Orientation of magnet with Lehman setup?
From: ChrisAtUpw@.......
Date: Sat, 3 Feb 2007 18:12:18 EST
In a message dated 03/02/2007, lehmancj@........... writes:
You mention your design has the coil on the boom, and magnet on the
ground. That is quite ok I guess, but I have never understood the advantage
over the coil on the ground - with the coil on the ground, the boom is free
of any attachments..... Maybe I am missing something---
Hi Jim,
There are several different situations if you mount a magnet on the
boom, use an iron mass, or make the boom from steel, some of which are worse than
others. You are very likely to be sensitive to magnetic field changes, or to
changes in the field gradient, all of which can result in unwanted noise.
You don't have to use magnetic components! It is advisable to 'design out' such
problems in the first place where possible, rather than having to 'find and
eliminate' them later on. Commercial mechanical seismometers are usually
designed with integral magnetic shielding - even the Ni-SpanC springs are
magnetic.
The principle effects are due to changes in the Earth's field, to the
magnetic attraction / field changes produced by cars, trucks, trains, kids
cycles, lawn mowers and especially to pulses on the utility power wiring in the
house. TVs, refrigerators, cookers and central heating systems are common
culprits. A seismometer is extremely sensitive - it doesn't take much force to
move the arm by over 50 nano metres!
You may pick up RF noise / static with the sensor coil / onto the
wiring. I favour the quad NdFeB magnet arrangement on mild steel backing plates for
producing the sensor field. This construction shields the pick up coil from
both external magnetic and electric fields and you don't need very large
coils.
Co-axial microphone cable gives good screening. I use the sort which has
a black plastic conducting layer in between the woven screen and the central
polythene insulation. This reduces signals due to vibration / cable movement
/ thermal expansion.
Regards,
Chris Chapman
In a message dated 03/02/2007, lehmancj@........... writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20
size=3D2> You mention your design has the coil on the boom, an=
d=20
magnet on the ground. That is quite ok I guess, but I have never=20
understood the advantage over the coil on the ground - with the coil on=
the=20
ground, the boom is free of any attachments..... Maybe I am missing=20
something---
Hi Jim,
There are several different situations if you m=
ount=20
a magnet on the boom, use an iron mass, or make the boom from steel, so=
me=20
of which are worse than others. You are very likely to be sensitive to magne=
tic=20
field changes, or to changes in the field gradient, all of which can re=
sult=20
in unwanted noise. You don't have to use magnetic components! It is advisabl=
e to=20
'design out' such problems in the first place where possible, rather than ha=
ving=20
to 'find and eliminate' them later on. Commercial mechanical seismomete=
rs=20
are usually designed with integral magnetic shielding - even the Ni-SpanC=20
springs are magnetic.
The principle effects are due to changes in the=
=20
Earth's field, to the magnetic attraction / field changes produced by c=
ars,=20
trucks, trains, kids cycles, lawn mowers and especially to pulses on the uti=
lity=20
power wiring in the house. TVs, refrigerators, cookers and central heat=
ing=20
systems are common culprits. A seismometer is extremely sensitive - it doesn=
't=20
take much force to move the arm by over 50 nano metres!
You may pick up RF noise / static with the sens=
or=20
coil / onto the wiring. I favour the quad NdFeB magnet arrangement on mild s=
teel=20
backing plates for producing the sensor field. This construction shields the=
=20
pick up coil from both external magnetic and electric fields and you don't n=
eed=20
very large coils.
Co-axial microphone cable gives good screening.=
I=20
use the sort which has a black plastic conducting layer in between the woven=
=20
screen and the central polythene insulation. This reduces signals due t=
o=20
vibration / cable movement / thermal expansion.
Regards,
Chris Chapman
Subject: Re: Orientation of magnet with Lehman setup?
From: "Connie and Jim Lehman" lehmancj@...........
Date: Sun, 4 Feb 2007 07:47:29 -0500
CHRIS--thanks for the info--very logical--I remember a project where we =
aligned a suspended magnet freely in the Earth's field and slightly =
stressed its position with another magnet nearby. This was in an =
attempt to note changes in the Earth's field with time due to Sun's =
activity etc.--well, the building "chiller" used to cycle on & off, =
about 100 ft. away, and we could sense that activity. WWV in those days =
gave the solar flux index which was a reference for such activity. We =
never had any definitive results!!!
As ever, Jim
----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Saturday, February 03, 2007 6:12 PM
Subject: Re: Orientation of magnet with Lehman setup?
In a message dated 03/02/2007, lehmancj@........... writes:
You mention your design has the coil on the boom, and magnet on =
the
ground. That is quite ok I guess, but I have never understood the =
advantage
over the coil on the ground - with the coil on the ground, the boom =
is free
of any attachments..... Maybe I am missing something---
Hi Jim,
There are several different situations if you mount a magnet on =
the boom, use an iron mass, or make the boom from steel, some of which =
are worse than others. You are very likely to be sensitive to magnetic =
field changes, or to changes in the field gradient, all of which can =
result in unwanted noise. You don't have to use magnetic components! It =
is advisable to 'design out' such problems in the first place where =
possible, rather than having to 'find and eliminate' them later on. =
Commercial mechanical seismometers are usually designed with integral =
magnetic shielding - even the Ni-SpanC springs are magnetic.=20
The principle effects are due to changes in the Earth's field, to =
the magnetic attraction / field changes produced by cars, trucks, =
trains, kids cycles, lawn mowers and especially to pulses on the utility =
power wiring in the house. TVs, refrigerators, cookers and central =
heating systems are common culprits. A seismometer is extremely =
sensitive - it doesn't take much force to move the arm by over 50 nano =
metres!
You may pick up RF noise / static with the sensor coil / onto the =
wiring. I favour the quad NdFeB magnet arrangement on mild steel backing =
plates for producing the sensor field. This construction shields the =
pick up coil from both external magnetic and electric fields and you =
don't need very large coils.=20
Co-axial microphone cable gives good screening. I use the sort =
which has a black plastic conducting layer in between the woven screen =
and the central polythene insulation. This reduces signals due to =
vibration / cable movement / thermal expansion.=20
Regards,
Chris Chapman
CHRIS--thanks for the info--very logical--I remember a project =
where we=20
aligned a suspended magnet freely in the Earth's field and slightly =
stressed its=20
position with another magnet nearby. This was in an attempt =
to note=20
changes in the Earth's field with time due to Sun's activity etc.--well, =
the=20
building "chiller" used to cycle on & off, about 100 ft. away, and =
we could=20
sense that activity. WWV in those days gave the solar flux index =
which was=20
a reference for such activity. We never had any definitive=20
results!!!
Subject: Re: Orientation of =
magnet with=20
Lehman setup?
In a message dated 03/02/2007, lehmancj@........... =
writes:
You mention your design has the coil on the =
boom, and=20
magnet on the ground. That is quite ok I guess, but I have =
never=20
understood the advantage over the coil on the ground - with the =
coil on=20
the ground, the boom is free of any attachments..... Maybe I am =
missing=20
something---
Hi Jim,
There are several different situations if =
you=20
mount a magnet on the boom, use an iron mass, or make the boom =
from=20
steel, some of which are worse than others. You are very likely to be=20
sensitive to magnetic field changes, or to changes in the field=20
gradient, all of which can result in unwanted noise. You don't =
have to=20
use magnetic components! It is advisable to 'design out' such problems =
in the=20
first place where possible, rather than having to 'find and =
eliminate'=20
them later on. Commercial mechanical seismometers are usually designed =
with=20
integral magnetic shielding - even the Ni-SpanC springs are magnetic. =
The principle effects are due to changes =
in the=20
Earth's field, to the magnetic attraction / field changes produced=20
by cars, trucks, trains, kids cycles, lawn mowers and especially =
to=20
pulses on the utility power wiring in the house. TVs, refrigerators,=20
cookers and central heating systems are common culprits. A =
seismometer is=20
extremely sensitive - it doesn't take much force to move the arm by =
over 50=20
nano metres!
You may pick up RF noise / static with =
the sensor=20
coil / onto the wiring. I favour the quad NdFeB magnet arrangement on =
mild=20
steel backing plates for producing the sensor field. This construction =
shields=20
the pick up coil from both external magnetic and electric fields and =
you don't=20
need very large coils.
Co-axial microphone cable gives good =
screening. I=20
use the sort which has a black plastic conducting layer in between the =
woven=20
screen and the central polythene insulation. This reduces signals =
due to=20
vibration / cable movement / thermal expansion.
Regards,
Chris=20
Chapman
Subject: Re: Digest from 02/03/2007 00:01:59
From: Randall Peters PETERS_RD@..........
Date: Sun, 04 Feb 2007 08:56:39 -0500
Hi Allan.
Your idea to 'float' your instrument was a stroke of genius, since it decouples local
tilt noises. I have posted your MKXXI paper at the top of my webpage
http://physics.mercer.edu/hpage/peters.html
where I expect it to start attracting a lot of attention. The Google guys love my
papers and I think they will find yours and post references to it on their search engine
in a prominent place. Like yourself, I am satisfied that you ARE seeing the earth's
eigenmodes. I've been observing them for many years, but the 'experts' refuse to
believe this is possible. After all, since the best (most expensive) instruments in the
world can't see what is routinely visible in the instruments produced by 'rank
amateurs'; then we 'must be seeing noise'!
The problem with the commercial instruments, as I have been trying to-no-avail to
point out to them for over a decade--is that their wonderful-for-earthquake instruments
do not function properly in the frequency range of the free oscillations. In spite of
the remarkable excellence of some of the ones you mentioned (when it comes to technology
designed around conventional wisdom) these folks are 'wearing blinders' in several key
areas. I view it as an 'inconvenient truth' for them.
Let me explain what I think we both are observing, that the pro's refuse to
consider. There are two obvious means for exciting eigenmodes, one type which they see,
and the other they refuse to consider. These are: (i) the ones everybody recognize
following large earthquakes, and (ii) the ones I postulated years ago (published by my
student Kwon). The latter I believe to be a class of oscillations that are unique and
generated by the following mechanism.
The earth is like a multiply-cracked hard-boiled egg. As it rotates under the tidal
forces, the 'shell' experiences 'snap, crackle, pops' that MUST excite the free
oscillations. They are not long-lived like the ones following the great Andaman-Sumatra
earthquake, as an example. Consequently, their linewidth is broader, according to the
uncertainty principle (Heisenberg's name appropriate to the understanding from a physics
perspective). Incidently, I am glad to see you reference A. A. Michelson in the context
of the tiltmeter physics. Don't know if you're aware of the fact that he won the Nobel
Prize in physics for the interferometer he designed (he was also a graduate of the Naval
Academy). When I was a visiting professor at West Point I saw one of his lab
notebooks. The calligraphy-like description of the experiments being performed told me
much about his careful attention to details!
One thing for you to keep in mind--there is no noise source of traditional (random)
type capable of generating spectral "doublets", such as you show in one of your
plots--corresponding to the modes S07 & 0T13 / S04 & 0S12. I saw other examples of the
same thing in your plots--which are very similar to ones that I have been observing for
about 15 years now. I am delighted that you have come to the same place with an
ingenious instrument that should allow some correlation tests. When I was at Texas Tech
University years ago, one of the geoscience professors there indicated what I knew (and
continue to hear from other pro's) is the following--if we can show that your instrument
and mine, separated by 2000+ miles, are oscillating at the same mHz frequencies; then
nobody who is rational stands positioned to dispute our claims.
You mentioned your desire to extend your spectral plots below 1 mHz. Larry
Cochrane has already done that for me, and I am sure he will give you the updated
WinQuake with which to do the same. It requires, for plotting, that you export the
spectral data and then view it with Excel. I will be happy to share particulars of the
method with you. One of the other nice features of the Excel graphs is that you can
plot versus frequency rather than log-frequency (the eigenmode spectral lines show up
better this way).
Thanks for sharing your results with me,
Randall
Subject: Re: Digest from 02/02/2007 00:01:26
From: Randall Peters PETERS_RD@..........
Date: Sun, 04 Feb 2007 09:54:56 -0500
Jerry,
I have been using Amaseis to collect data on two of my instruments--(i) one being a
modified Sprengnether vertical with unconventional force feedback (a long time-constant
integrator for "soft"-force feedback as opposed to "hard" force balance), and (ii) the
long-period pendulum that I have mentioned previously to the listserve ('hare-brained'
but useful idea involving an undamped instrument). Of course both instruments are
limited by the 16-bit Amaseis. However, I am 'feeding' Amaseis by means of a wonderful,
inexpensive 24-bit adc system built by Symmetric Research. Kip Weiss (with his
programmer Wendy) produced for me a program called Amasend98. Operating with a
null-modem serial cable, one can select from the 24-bits out of the PAR1CH--the 16-bit
segment with which to operate. By this means I generate and save *.sac files that can
be opened by WinQuake by doing nothing more than clicking on them. I stand in amazement
at the user-friendliness/power of the codes developed by Larry Cochrane!
I have found some remarkably useful synergetic features of using WinQuake and
Amaseis interchangeably. For example, Amaseis does spectra without log-frequency or
log-magnitude; whereas the plots of WinQuake are log-log. The advantages of one over the
other depend largely on the frequency range of interest. For 'usual' stuff, the log-log
plots are preferred; however, for eigenmode oscillation studies, the linear ones prove
better for my purposes. Also, Amaseis has a truly powerful, user friendly feature--the
ability, while holding down the left button of the mouse, to scan over and select for
memory, a record piece according to features of interest.
Randall
Subject: WinSDR vs. AmaSys Software
From: "Jerry Payton"
Date: Fri, 2 Feb 2007 10:49:52 -0600
This is a multi-part message in MIME format.
------=_NextPart_000_0029_01C746B7.DDF30800
Content-Type: text/plain;
charset="Windows-1252"
Content-Transfer-Encoding: 7bit
I was just curious (for experimental and comparison purposes) if AmaSys
software would ingest and display sensor signals via Larry Cochrane's
electronics package? Anybody ever tried?
Regards,
Jerry Payton
Subject: Re: Orientation of magnet with Lehman setup?
From: "Thomas Dick" dickthomas01@.............
Date: Sun, 4 Feb 2007 09:09:31 -0600
Gentlemen, Chris is right -- the magnet must remain stationary. I am =
living proof. Dr. Peters might escape the common pitfalls in his unique =
lab situation but the "common people" are not going to be that lucky. To =
name some of the things that will distort your data that you probably =
haven't seen. 1. electromagnetic rays from commerical transmitters such =
as CB's going by in cars 200 ft away. Amateur radio equipment as high as =
2 meters and with a power of less than five watts causes "episodes". I =
ran a ten meter repeater here (transmitter put out 250 watts) for 25 yrs =
but seismology put an end to that. My transmitter for operation on all =
bands below ten meters puts out 100 watts and the antennas are full =
sized. I still could distort the data. 2. the normal things (that Chris =
always alludes to); motors, fan blowers, even carpenters using portable =
generators 3. lightning 4. incoming power line noise -- I had my line =
check and you wouldn't believe what was there 5. finally, I am =
absolutely sure that I detected the magnetic disturbance within a =
megacell thunderstorm that brought a F3 tornado within nine miles of my =
location two years ago. Here is one reference (not the best) =
http://www.straightdope.com/classics/a1_166b.html . The public was urged =
to use this method in the early days of TV before cable and modern =
tuners -- probably before most of you were borned. It has no value =
today. 6. sun spots - the last two cycles haven't really been "the =
best". Plus there are solar flares. They come and are gone. Oh, yes, I =
even tried metal mesh screening with magnets on the screens to help =
shield. My words, take the road most suggested.
Gentlemen, Chris is right -- the magnet must remain stationary. I =
am living=20
proof. Dr. Peters might escape the common pitfalls in his unique lab =
situation=20
but the "common people" are not going to be that lucky. To name some of =
the=20
things that will distort your data that you probably haven't seen. 1.=20
electromagnetic rays from commerical transmitters such as CB's going by =
in cars=20
200 ft away. Amateur radio equipment as high as 2 meters and with a =
power of=20
less than five watts causes "episodes". I ran a ten meter repeater here=20
(transmitter put out 250 watts) for 25 yrs but seismology put an end to =
that. My=20
transmitter for operation on all bands below ten meters puts out 100 =
watts and=20
the antennas are full sized. I still could distort the data. 2. the =
normal=20
things (that Chris always alludes to); motors, fan blowers, even =
carpenters=20
using portable generators 3. lightning 4. incoming power line noise -- I =
had my=20
line check and you wouldn't believe what was there 5. finally, I am =
absolutely=20
sure that I detected the magnetic disturbance within a megacell =
thunderstorm=20
that brought a F3 tornado within nine miles of my location two years =
ago. Here=20
is one reference (not the best) http://www.str=
aightdope.com/classics/a1_166b.html .=20
The public was urged to use this method in the early days of =
TV before=20
cable and modern tuners -- probably before most of you were borned. =
It has=20
no value today. 6. sun spots - the last two cycles haven't really been =
"the=20
best". Plus there are solar flares. They come and are gone. Oh, yes, I =
even=20
tried metal mesh screening with magnets on the screens to help shield. =
My words,=20
take the road most suggested.
Subject: Re: WinSDR vs. AmaSeis Software
From: Bobhelenmcclure@.......
Date: Fri, 9 Feb 2007 17:31:21 EST
Hi Randall Peters,
You said,
"I have found some remarkably useful synergetic features of using WinQuake
and
Amaseis interchangeably. For example, Amaseis does spectra without
log-frequency or
log-magnitude; whereas the plots of WinQuake are log-log."
My version of Amaseis can do both linear and log-log plots. The FFT tab
clearly shows a choice between linear and log-log display. Maybe you need to
update.
Bob
Hi Randall Peters,
You said,
"I have found some remarkably useful synergetic feat=
ures=20
of using WinQuake and Amaseis interchangeably. For example, Amaseis=
=20
does spectra without log-frequency or log-magnitude; whereas the plots of=
=20
WinQuake are log-log."
My version of Amaseis can do both linear and log-log plots. The=20=
FFT=20
tab clearly shows a choice between linear and log-log display. Maybe you nee=
d to=20
update.
Bob
Subject: popsicle stick seismometer?
From: "David Saum" DSaum@............
Date: Sat, 10 Feb 2007 10:05:03 -0500
Any ideas for a popsicle stick seismometer?
See request below.
Ciao,
Dave
----- Original Message -----
From: "Daisy Torres"
To:
Sent: Friday, February 09, 2007 4:39 PM
Subject: HELLO
> HI I ACTUALLY HAVE TO MAKE A SEISMOGRAPH FOR SCHOOL. MY TEACHER TOLD ME I
> COULD DO IT OUT OF POPSICLE STICKS (WHICH I WANT TO DO IT OUT OF).
> BUT I LOOK AT ALL THIS HEAVY STUFF LIKE WOOD THAT SUPPOSABLY THATS HOW
> YOU DO ONE. BUT I DONT HAVE THAT MAATERIAL AND REALLY DONT WANT TO DO IT
> OUT OF NONE OF THAT STUFF. AND I DONT KNOW HOW TO DO ONE. IM VERY
> CONFUSED.
> WHAT CAN I DO IT OUT OFF?
> (LIKE POPSICLE STICKS) IF I CAN HOW?
> "REMEMBER IM ONLY IN 8TH GRADE.
> PLEASE RESPOND AS SOON AS POSSIBLE, PLAESE!!!!
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: popsicle stick seismometer?
From: John or Jan Lahr JohnJan@........
Date: Sat, 10 Feb 2007 08:23:27 -0800
Dear Daisy,
It is possible to build a seismometer out of inexpensive and easy to
work with items such as popsicle sticks and paper cups. Here's a
picture from a workshop for teachers where they are doing just that:
http://jclahr.com/science/earth_science/northridge_2007/photos/target0.html
There are some added pictures here:
http://www.iris.edu/about/ENO/iows/2_2004b.htm
This page gives the basic instructions:
http://www.howstuffworks.com/framed.htm?parent=question142.htm&url=http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/Seismograph.html
UC Berkeley provides ideas for a slightly more elaborate but still
quite easy to build seismometer:
http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/Seismograph.html
Most important, have some fun with this and try to come up with your
own design. Send me a picture when your project is done, or post a
picture on your school web site so that I can see it.
Yours,
John Lahr
>----- Original Message ----- From: "Daisy Torres"
>To:
>Sent: Friday, February 09, 2007 4:39 PM
>Subject: HELLO
>
>
>>HI I ACTUALLY HAVE TO MAKE A SEISMOGRAPH FOR SCHOOL. MY TEACHER
>>TOLD ME I COULD DO IT OUT OF POPSICLE STICKS (WHICH I WANT TO DO IT OUT OF).
>> BUT I LOOK AT ALL THIS HEAVY STUFF LIKE WOOD THAT SUPPOSABLY
>> THATS HOW YOU DO ONE. BUT I DONT HAVE THAT MAATERIAL AND REALLY
>> DONT WANT TO DO IT OUT OF NONE OF THAT STUFF. AND I DONT KNOW HOW
>> TO DO ONE. IM VERY CONFUSED.
>> WHAT CAN I DO IT OUT OFF?
>> (LIKE POPSICLE STICKS) IF I CAN HOW?
>> "REMEMBER IM ONLY IN 8TH GRADE.
>> PLEASE RESPOND AS SOON AS POSSIBLE, PLAESE!!!!
>
#################################/ John C. Lahr
################################/ Emeritus Seismologist
###############################/ U.S. Geological Survey
==========================/ Central Region Geologic Hazards Team
#############################//#################################
############################//##################################
PO Box 548 /###################################
Corvallis, Oregon 97339 /===============================
Phone: (541) 758-2699 /####################################
Cell: (541) 740-4844 /#####################################
Fax: (413) 658-2699 /######################################
johnjan@........ /#######################################
http://jclahr.com/science/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Digest from 02/09/2007 00:00:07
From: Randall Peters PETERS_RD@..........
Date: Sat, 10 Feb 2007 11:30:37 -0500
Thanks, Bob, for pointing this out to me.
I downloaded the update and now have this very useful feature of selecting
between linear and log-log plots of spectra. This increases the flexibility of
Amaseis considerably, especially in the low frequency realm where I hope that many
of you will follow Allan Coleman's lead. Kudo's to Alan Jones for providing this
additional capability to his outstanding software.
Incidently, I have been using Amaseis to both collect and analyze some pendulum
data as part of my research of low-level anharmonicity. Those who are interested
might want to look at the Mercer Physics department webpage announcement concerning
the seminar I will be giving next week
http://physics.mercer.edu/seminars/default.htm
Something I just noted (don't know whether it was available on the earlier
version of Amaseis)--is a very useful additional feature of the code; i.e., the
ability to read-off (by cursor placement with the mouse) the FFT magnitude as well
as the frequency of a spectral line. This is of great value when it comes to
estimating the quality factor of a pendulum in free-decay using the so-called
"short time-Fourier-transform" (STFT). One can 'step through' the record manually
to accomplish what is typically an automated process as in routines like LabView.
About my comments concerning the synergy of Amaseis and WinQuake when used
interchangeably--even with the Amaseis upgrade, I still find some significant
advantages to using the two of them in this way. To my knowledge, Amaseis does not
presently allow for saving (exporting) the spectral data, whereas the version of
WinQuake that I am using does. I don't know if Larry has folded that capability
into the latest version of the code on his website. The reason data export is
valuable to me is because of the things I am able to do with the data once I have
loaded it into Excel. For example, one can then generate phase plots (numerically
generated velocity versus position), correlation plots between two different
records, etc, etc........ As much as I resist advertising Microsoft products, Excel
is in a class all its own! Its use opens up a lot of new possibilities for a
better understanding of seismology. One thing that I regularly compute with it are
power spectral densities, for which (at least to the extent linear assumptions are
valid) the results are independent of the specifics of the instrument that
collected the data.
What I see increasingly from the interchanges of this listserve is impressive
for the following reason--collectively we can advance seismology in ways that may
not even be possible for the professional science groups. At least in my career I
have not observed comparable means to facilitate advancement. The desire for
knowledge, devoid of unwarranted arrogance, that I have seen in listserve comments,
is a refreshing change from most of my experiences over the last forty years.
Randall
psn-l-digest-request@.............. wrote:
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ---- --.
> | Message 1 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: WinSDR vs. AmaSeis Software
> From: Bobhelenmcclure@.......
> Date: Fri, 9 Feb 2007 17:31:21 EST
>
> -------------------------------1171060281
> Content-Type: text/plain; charset="US-ASCII"
> Content-Transfer-Encoding: 7bit
>
> Hi Randall Peters,
>
> You said,
>
> "I have found some remarkably useful synergetic features of using WinQuake
> and
> Amaseis interchangeably. For example, Amaseis does spectra without
> log-frequency or
> log-magnitude; whereas the plots of WinQuake are log-log."
>
>
> My version of Amaseis can do both linear and log-log plots. The FFT tab
> clearly shows a choice between linear and log-log display. Maybe you need to
> update.
>
> Bob
>
> -------------------------------1171060281
> Content-Type: text/html; charset="US-ASCII"
> Content-Transfer-Encoding: quoted-printable
>
>
>
>
>
> Arial"=20
> bottomMargin=3D7 leftMargin=3D7 topMargin=3D7 rightMargin=3D7> e_document=20
> face=3DArial color=3D#000000 size=3D2> color=3D#000000=20
> size=3D2> T=20
> id=3Drole_document face=3DArial color=3D#000000 size=3D2> ument=20
> face=3DArial color=3D#000000 size=3D2>
>
Hi Randall Peters,
>
>
You said,
>
>
"I have found some remarkably useful synergetic feat=
> ures=20
> of using WinQuake and Amaseis interchangeably. For example, Amaseis=
> =20
> does spectra without log-frequency or log-magnitude; whereas the plots of=
> =20
> WinQuake are log-log."
>
>
>
My version of Amaseis can do both linear and log-log plots. The=20=
> FFT=20
> tab clearly shows a choice between linear and log-log display. Maybe you nee=
> d to=20
> update.
>
>
Bob
>
> -------------------------------1171060281--
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-DIGEST-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
Subject: Re: popsicle stick seismometer?
From: shammon1@.............
Date: Sat, 10 Feb 2007 08:34:07 -0800 (GMT-08:00)
Build a hanging gate style seismograph. Form an L with two sticks using four thin strips of fine silk treads glued in an x pattern --- x --- to form the hinge as you would in a model airplane tail hinge. Glue a small mass weight using a washer or two at the end of the horizontal stick. Push the vertical stick in the ground. Mark the location under the stick and wait for an event.
Regards, Steve Hammond PSN San Jose, Aptos CA
-----Original Message-----
>From: David Saum
>Sent: Feb 10, 2007 7:05 AM
>To: psn-l@..............
>Subject: popsicle stick seismometer?
>
>
>Any ideas for a popsicle stick seismometer?
>
>See request below.
>
>Ciao,
>
>Dave
>
>----- Original Message -----
>From: "Daisy Torres"
>To:
>Sent: Friday, February 09, 2007 4:39 PM
>Subject: HELLO
>
>
>> HI I ACTUALLY HAVE TO MAKE A SEISMOGRAPH FOR SCHOOL. MY TEACHER TOLD ME I
>> COULD DO IT OUT OF POPSICLE STICKS (WHICH I WANT TO DO IT OUT OF).
>> BUT I LOOK AT ALL THIS HEAVY STUFF LIKE WOOD THAT SUPPOSABLY THATS HOW
>> YOU DO ONE. BUT I DONT HAVE THAT MAATERIAL AND REALLY DONT WANT TO DO IT
>> OUT OF NONE OF THAT STUFF. AND I DONT KNOW HOW TO DO ONE. IM VERY
>> CONFUSED.
>> WHAT CAN I DO IT OUT OFF?
>> (LIKE POPSICLE STICKS) IF I CAN HOW?
>> "REMEMBER IM ONLY IN 8TH GRADE.
>> PLEASE RESPOND AS SOON AS POSSIBLE, PLAESE!!!!
>
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with
>the body of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: STFT and PSD
From: John or Jan Lahr JohnJan@........
Date: Sat, 10 Feb 2007 10:48:31 -0800
Randall,
The STFT sounds useful, but I'm not sure what it is.
Also, could you share your spread sheet for computing the PSD? That
quantity has always left me scratching my head. Maybe if I played around
with it a bit, I would be able to appreciate/understand it better.
Thanks,
John
At 08:30 AM 2/10/2007, you wrote:
>Thanks, Bob, for pointing this out to me.
> I downloaded the update and now have this very useful feature of selecting
>between linear and log-log plots of spectra. This increases the
>flexibility of
>Amaseis considerably, especially in the low frequency realm where I
>hope that many
>of you will follow Allan Coleman's lead. Kudo's to Alan Jones for
>providing this
>additional capability to his outstanding software.
>Incidently, I have been using Amaseis to both collect and analyze
>some pendulum
>data as part of my research of low-level anharmonicity. Those who
>are interested
>might want to look at the Mercer Physics department webpage
>announcement concerning
>the seminar I will be giving next week
>http://physics.mercer.edu/seminars/default.htm
> Something I just noted (don't know whether it was available on
> the earlier
>version of Amaseis)--is a very useful additional feature of the
>code; i.e., the
>ability to read-off (by cursor placement with the mouse) the FFT
>magnitude as well
>as the frequency of a spectral line. This is of great value when it comes to
>estimating the quality factor of a pendulum in free-decay using the so-called
>"short time-Fourier-transform" (STFT). One can 'step through' the
>record manually
>to accomplish what is typically an automated process as in routines
>like LabView.
> About my comments concerning the synergy of Amaseis and WinQuake when used
>interchangeably--even with the Amaseis upgrade, I still find some significant
>advantages to using the two of them in this way. To my knowledge,
>Amaseis does not
>presently allow for saving (exporting) the spectral data, whereas
>the version of
>WinQuake that I am using does. I don't know if Larry has folded
>that capability
>into the latest version of the code on his website. The reason data export is
>valuable to me is because of the things I am able to do with the
>data once I have
>loaded it into Excel. For example, one can then generate phase
>plots (numerically
>generated velocity versus position), correlation plots between two different
>records, etc, etc........ As much as I resist advertising Microsoft
>products, Excel
>is in a class all its own! Its use opens up a lot of new possibilities for a
>better understanding of seismology. One thing that I regularly
>compute with it are
>power spectral densities, for which (at least to the extent linear
>assumptions are
>valid) the results are independent of the specifics of the instrument that
>collected the data.
> What I see increasingly from the interchanges of this
> listserve is impressive
>for the following reason--collectively we can advance seismology in
>ways that may
>not even be possible for the professional science groups. At least
>in my career I
>have not observed comparable means to facilitate advancement. The desire for
>knowledge, devoid of unwarranted arrogance, that I have seen in
>listserve comments,
>is a refreshing change from most of my experiences over the last forty years.
>
> Randall
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: IRIS Wilber II
From: Bobhelenmcclure@.......
Date: Sat, 10 Feb 2007 20:11:15 EST
A memo to Larry Conklin and to others who might be interested.
Hi Larry,
You mentioned that you compare your data with PAL. I do also since they
are only 21km from me. Have you tried looking at BINY? They are closer to you.
WinQuake and Amaseis will open SAC binary files. You can download such
files from major events from almost any network station in the world easily from
IRIS at
_http://www.iris.washington.edu/_ (http://www.iris.washington.edu/)
Click on "Earthquakes" and "Wilber II" to get to the download page. BINY
belongs to the US network. Do not try to select an event using the picture
display. Go to the listings of events instead. After you have selected your
event and stations (you have to unselect almost everything), be sure you select
"SAC BINARY individual files" as the file format. Select BHZ, BHN, and BHE as
the channels. Give a user name and email address. Elect to have an email sent
when processing is complete. If you do not ask for many files, you will have
a high priority and will usually get your files prepared in a few minutes
after the request is entered.
I occasionally download events from PAL. My correspondence with their data
is remarkably close, once I have processed my data using my WQFilter
utility. Something is not right with the IIR filters in WinQuake. They have more
ringing and sharper cutoffs than they should, so I avoid using them. The FFT
filters are OK. Cochrane did not write the filter code himself. He lifted the
code from a book "Analog and Digital Filter Design using C" by Les Thede,
which is no longer in print.
The filters in Amaseis are OK. Both Dr. Jones and I worked out the
algorithms for Butterworth filters and ended up with identical results. I gave him
my algorithm for the period extending filter, and his filter performance
agrees with mine. I do have an optional back-and-forth filter pass capability,
which yields zero distortion filtering, equivalent to FFT filtering. Amaseis
does not implement that.
If you should want to convert PSN files to SAC binary format, WinQuake can
do that. However, there is a bug in WinQuake that prevents transfer of event
time. I am able to patch in a correction on the files I convert. I told
Cochrane what was wrong, but he has essentially retired from maintaining his
software, after a lifetime of good and dedicated work.
I am almost done with a heliplot program that filters and displays WinDaq
log files, including the one currently open, up to 27 hours before the
present hour or any lesser number of hours.
Regards,
Bob
A memo to Larry Conklin and to others who might be interested.
Hi Larry,
You mentioned that you compare your data with PAL. I do also sin=
ce=20
they are only 21km from me. Have you tried looking at BINY? They are closer=20=
to=20
you.
WinQuake and Amaseis will open SAC binary files. You can downloa=
d=20
such files from major events from almost any network station in the world ea=
sily=20
from IRIS at
http://www.iris.washington.edu/=
Click on "Earthquakes" and "Wilber II" to get to the download=20
page. BINY belongs to the US network. Do not try to select an event usi=
ng=20
the picture display. Go to the listings of events instead. After you have=20
selected your event and stations (you have to unselect almost everything), b=
e=20
sure you select "SAC BINARY individual files" as the file format. Select BHZ=
,=20
BHN, and BHE as the channels. Give a user name and email address. Elect to h=
ave=20
an email sent when processing is complete. If you do not ask for many files,=
you=20
will have a high priority and will usually get your files prepared in a few=20
minutes after the request is entered.
I occasionally download events from PAL. My correspondence with=20
their data is remarkably close, once I have processed my data using my WQFil=
ter=20
utility. Something is not right with the IIR filters in WinQuake. They have=20=
more=20
ringing and sharper cutoffs than they should, so I avoid using them. The FFT=
=20
filters are OK. Cochrane did not write the filter code himself. He lifted th=
e=20
code from a book "Analog and Digital Filter Design using C" by Le=
s=20
Thede, which is no longer in print.
The filters in Amaseis are OK. Both Dr. Jones and I worked=20=
out=20
the algorithms for Butterworth filters and ended up with identical results.=20=
I=20
gave him my algorithm for the period extending filter, and his filter=20
performance agrees with mine. I do have an optional back-and-forth filt=
er=20
pass capability, which yields zero distortion filtering, equivalent to FFT=20
filtering. Amaseis does not implement that.
If you should want to convert PSN files to SAC binary forma=
t,=20
WinQuake can do that. However, there is a bug in WinQuake that prevents tran=
sfer=20
of event time. I am able to patch in a correction on the files I convert. I=20=
told=20
Cochrane what was wrong, but he has essentially retired=20
from maintaining his software, after a lifetime of good and dedicated=20
work.
I am almost done with a heliplot program that filters and displa=
ys=20
WinDaq log files, including the one currently open, up to 27 hours before th=
e=20
present hour or any lesser number of hours.
Regards,
Bob
Subject: Re: popsicle stick seismometer?
From: Angel sismos@..............
Date: Sun, 11 Feb 2007 02:45:38 +0000
Hello David,
Maybe instead of a popsicle stick a single hacksaw blade can be made
into a vertical. a magnet at the end a coil near by and a sensitive
voltmeter.
angel
Saturday, February 10, 2007, 3:05:03 PM, you wrote:
> Any ideas for a popsicle stick seismometer?
> See request below.
> Ciao,
> Dave
> ----- Original Message -----
> From: "Daisy Torres"
> To:
> Sent: Friday, February 09, 2007 4:39 PM
> Subject: HELLO
>> HI I ACTUALLY HAVE TO MAKE A SEISMOGRAPH FOR SCHOOL. MY TEACHER TOLD ME I
>> COULD DO IT OUT OF POPSICLE STICKS (WHICH I WANT TO DO IT OUT OF).
>> BUT I LOOK AT ALL THIS HEAVY STUFF LIKE WOOD THAT SUPPOSABLY THATS HOW
>> YOU DO ONE. BUT I DONT HAVE THAT MAATERIAL AND REALLY DONT WANT TO DO IT
>> OUT OF NONE OF THAT STUFF. AND I DONT KNOW HOW TO DO ONE. IM VERY
>> CONFUSED.
>> WHAT CAN I DO IT OUT OFF?
>> (LIKE POPSICLE STICKS) IF I CAN HOW?
>> "REMEMBER IM ONLY IN 8TH GRADE.
>> PLEASE RESPOND AS SOON AS POSSIBLE, PLAESE!!!!
> __________________________________________________________
> Public Seismic Network Mailing List (PSN-L)
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
--
Best regards,
Angel
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Exporting FFT data
From: Roger Sparks rsparks@..........
Date: Sun, 11 Feb 2007 08:14:55 -0800
Good Morning All,
Dr. Randall Peters writes "
To my knowledge, Amaseis does not
presently allow for saving (exporting) the spectral data, whereas the version of
WinQuake that I am using does. I don't know if Larry has folded that capability
into the latest version of the code on his website."
My latest version of WinQuake does not export the data from the FFT analysis but does save the screen containing the output as a "gif" file. It sounds like Dr. Peters could use the data file so that he could further process the data.
Amaseis does not have any provision for recording FFT data or the screen. However, there is a way to accomplish a screen save containing the Amaseis FFT results. We can take advantage of the Windows "print screen" capability.
You will notice that every computer keyboard has a key labeled "Print Screen". When this key is pressed, the contents of the window (no matter what program is running) is saved to memory. Next, find and open the ancient program "Paint" which was included with the "Accessory" programs in all versions of Windows through Windows XP. Look in the "Edit" menu of Paint and you should see that the "Paste" label is active. Click "Paste" and the contents of memory (which should be the screen contents present when "Print Screen" was pressed) should appear in the Paint window. Paint can generate and save a "BMP" file which is a permanent record of the screen display.
Best wishes,
Roger
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Exporting FFT data
From: Pete Rowe ptrowe@.........
Date: Sun, 11 Feb 2007 09:42:22 -0800 (PST)
Hi everyone
I've been using a wonderful program called "Gadwin
PrintScreen 3.5"
It is from www.gadwin.com
It embodies just what the original IBM engineers
envisioned when they put the Print Screen button on
the keyboard. You push the button, the screen prints.
Nice! You can print to the printer or a file or both.
Get it.
Pete
--- Roger Sparks wrote:
> Good Morning All,
>
> Dr. Randall Peters writes "
>
> To my knowledge, Amaseis does not
> presently allow for saving (exporting) the spectral
> data, whereas the version of
> WinQuake that I am using does. I don't know if
> Larry has folded that capability
> into the latest version of the code on his website."
>
> My latest version of WinQuake does not export the
> data from the FFT analysis but does save the screen
> containing the output as a "gif" file. It sounds
> like Dr. Peters could use the data file so that he
> could further process the data.
>
> Amaseis does not have any provision for recording
> FFT data or the screen. However, there is a way to
> accomplish a screen save containing the Amaseis FFT
> results. We can take advantage of the Windows
> "print screen" capability.
>
> You will notice that every computer keyboard has a
> key labeled "Print Screen". When this key is
> pressed, the contents of the window (no matter what
> program is running) is saved to memory. Next, find
> and open the ancient program "Paint" which was
> included with the "Accessory" programs in all
> versions of Windows through Windows XP. Look in the
> "Edit" menu of Paint and you should see that the
> "Paste" label is active. Click "Paste" and the
> contents of memory (which should be the screen
> contents present when "Print Screen" was pressed)
> should appear in the Paint window. Paint can
> generate and save a "BMP" file which is a permanent
> record of the screen display.
>
> Best wishes,
>
> Roger
>
>
__________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email
> PSN-L-REQUEST@.............. with
> the body of the message (first line only):
> unsubscribe
> See http://www.seismicnet.com/maillist.html for more
> information.
>
____________________________________________________________________________________
Food fight? Enjoy some healthy debate
in the Yahoo! Answers Food & Drink Q&A.
http://answers.yahoo.com/dir/?link=list&sid=396545367
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Mystery Noise
From: "tchannel" tchannel@..............
Date: Sun, 11 Feb 2007 11:28:17 -0700
I received some Mystery noise yesterday 3:20pm and again today at =
8:40am. This noise is different than the road construction of a few =
months ago.
It appears as single spikes, spaced one minute apart, all the same in =
height. On the helicorer they look like fence posts. eight the first =
time and eleven today. I drove around the neighbor hood but did not =
see anything. Happy to email a screenshot, etc to anyone who might =
have an idea.
Thanks, Ted
I received some Mystery noise =
yesterday=20
3:20pm and again today at 8:40am. This noise is different than the =
road=20
construction of a few months ago.
It appears as single spikes, spaced one =
minute=20
apart, all the same in height. On the helicorer they look like =
fence=20
posts. eight the first time and eleven today. I drove =
around=20
the neighbor hood but did not see anything. Happy to email a =
screenshot, etc to anyone who might have an idea.
Thanks, Ted
Subject: Re: Mystery Noise
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sun, 11 Feb 2007 18:32:38 +0000
Hi
Can you email me a gif image of the noise ? It would also be intresting
to know what Hz level it's on.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Mystery Noise
From: ChrisAtUpw@.......
Date: Sun, 11 Feb 2007 13:44:06 EST
In a message dated 11/02/2007, tchannel@.............. writes:
I received some Mystery noise yesterday 3:20pm and again today at 8:40am.
This noise is different than the road construction of a few months ago.
It appears as single spikes, spaced one minute apart, all the same in
height. On the helicorer they look like fence posts. eight the first time and
eleven today. I drove around the neighbor hood but did not see anything. Happy to
email a screenshot, etc to anyone who might have an idea.
Hi Ted,
Are they all of the same duration and what is it? How many channels are
you recording and is it on all of them? This sounds more like a timing
problem / poor circuit board contact / psu supply fault / faulty chip / earth
contact / loop problem. Check the GPS reception?
Regards,
Chris Chapman
In a message dated 11/02/2007, tchannel@.............. writes:
I received some Mystery noise yest=
erday=20
3:20pm and again today at 8:40am. This noise is different than the r=
oad=20
construction of a few months ago.
It appears as single spikes, spaced one m=
inute=20
apart, all the same in height. On the helicorer they look like fence posts=
..=20
eight the first time and eleven today. I drove around the neighbor ho=
od=20
but did not see anything. Happy to email a screenshot, etc to anyone=20=
who=20
might have an idea.
Hi Ted,
Are they all of the same duration and what is i=
t?=20
How many channels are you recording and is it on all of them? This sounds mo=
re=20
like a timing problem / poor circuit board contact / psu supply fault / faul=
ty=20
chip / earth contact / loop problem. Check the GPS reception?
Regards,
Chris Chapman
Subject: WinSDR A/D board question
From: "Bob Hammond" propgrinder@.........
Date: Sun, 11 Feb 2007 11:05:21 -0900
Anyone (Larry?) know if the power LED on the A/D board should blink on/off
when the GPS adapter board is sending 1PPS? It's been so long since I
looked that I've forgotten.
I've lost my 1PPS somehow and am troubleshooting it. The GPS LED is
blinking at 1PPS but I'm not getting it at WinSDR.
Bob Hammond
Public Seismic Network - Alaska
http://wulik.com
Anyone (Larry?) know if the power LED on the A/D board should blink on/off when the GPS adapter board is sending 1PPS? It's been so long since I looked that I've forgotten.
I've lost my 1PPS somehow and am troubleshooting it. The GPS LED is blinking at 1PPS but I'm not getting it at WinSDR.
Subject: Re: popsicle stick seismometer?
From: John or Jan Lahr JohnJan@........
Date: Sun, 11 Feb 2007 15:32:48 -0800
Hi Daisy,
Some of the teachers developed "seimoscopes." You can read about the
earliest one developed in China here:
http://inventors.about.com/library/inventors/blseismograph2.htm
Here's another design more like the one you probably have in mind:
http://jclahr.com/science/earth_science/model_seismograph/index.html
It doesn't use popsicle sticks, but it's probably clearer how it works.
Good luck!
John
At 12:14 PM 2/11/2007, you wrote:
>HI WAS NOT QUITE SURE WHAT THE FIRST PICTURE BELOW HAD. I KNOW IT
>HAS WOOD AT THE BOTTOM, PEN, PAPER PLATE, AND ARENT SURE WHAT THE
>OTHER MATERIALS ARE. COULD YOU HELP ME OUT AND TELL WHAT THEY ARE.
> ALSO THAT IS A SEISMOGRAPH RIGHT?
>O YEAH IF IT IS, DONT SEISMOGRAPHS HAVE A HEAVY PART?
>AND WERE WOULD THE FAXING PAPER GO, OR YOU KNOW THE PAPER WERE IT
>MARKS EVRYTHING DOWN WITH THE PEN.
>
>
>John or Jan Lahr wrote:
>Dear Daisy,
>
>It is possible to build a seismometer out of inexpensive and easy to
>work with items such as popsicle sticks and paper cups. Here's a
>picture from a workshop for teachers where they are doing just that:
>http://jclahr.com/science/earth_science/northridge_2007/photos/target0.html
>There are some added pictures here:
>http://www.iris.edu/about/ENO/iows/2_2004b.htm
>This page gives the basic instructions:
>http://www.howstuffworks.com/framed.htm?parent=question142.htm&url=http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/Seismograph.html
>
>UC Berkeley provides ideas for a slightly more elaborate but still
>quite easy to build seismometer:
>http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/Seismograph.html
>
>Most important, have some fun with this and try to come up with your
>own design. Send me a picture when your project is done, or post a
>picture on your school web site so that I can see it.
>
>Yours,
>John Lahr
>
>
> >----- Original Message ----- From: "Daisy Torres"
> >To:
> >Sent: Friday, February 09, 2007 4:39 PM
> >Subject: HELLO
> >
> >
> >>HI I ACTUALLY HAVE TO MAKE A SEISMOGRAPH FOR SCHOOL. MY TEACHER
> >>TOLD ME I COULD DO IT OUT OF POPSICLE STICKS (WHICH I WANT TO DO
> IT OUT OF).
> >> BUT I LOOK AT ALL THIS HEAVY STUFF LIKE WOOD THAT SUPPOSABLY
> >> THATS HOW YOU DO ONE. BUT I DONT HAVE THAT MAATERIAL AND REALLY
> >> DONT WANT TO DO IT OUT OF NONE OF THAT STUFF. AND I DONT KNOW HOW
> >> TO DO ONE. IM VERY CONFUSED.
> >> WHAT CAN I DO IT OUT OFF?
> >> (LIKE POPSICLE STICKS) IF I CAN HOW?
> >> "REMEMBER IM ONLY IN 8TH GRADE.
> >> PLEASE RESPOND AS SOON AS POSSIBLE, PLAESE!!!!
> >
>
>
>#################################/ John C. Lahr
>################################/ Emeritus Seismologist
>###############################/ U.S. Geological Survey
>==========================/ Central Region Geologic Hazards Team
>#############################//#################################
>############################//##################################
>PO Box 548 /###################################
>Corvallis, Oregon 97339 /===============================
>Phone: (541) 758-2699 /####################################
>Cell: (541) 740-4844 /#####################################
>Fax: (413) 658-2699 /######################################
>johnjan@........ /#######################################
>http://jclahr.com/science/
>
>
>
>
>TV dinner still cooling?
>Check out
>"Tonight's Picks" on Yahoo! TV.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: WinSDR A/D board question
From: "Stephen Hammond" shammon1@.............
Date: Sun, 11 Feb 2007 22:38:36 -0800
Yes, the GPS light blinks
Steve Hammond
-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@...............
On Behalf Of Bob Hammond
Sent: Sunday, February 11, 2007 12:05 PM
To: psn-l@..............
Subject: WinSDR A/D board question
Anyone (Larry?) know if the power LED on the A/D board should blink
on/off when the GPS adapter board is sending 1PPS? It's been so long
since I looked that I've forgotten.
I've lost my 1PPS somehow and am troubleshooting it. The GPS LED is
blinking at 1PPS but I'm not getting it at WinSDR.
Bob Hammond
Public Seismic Network - Alaska
http://wulik.com
Yes, the GPS light blinks =
Steve =
Hammond
-----Original =
Message----- From: =
psn-l-request@..............
[mailto:psn-l-request@............... On
Behalf Of Bob Hammond Sent: Sunday, February =
11, 2007
12:05 PM To: =
psn-l@.............. Subject: WinSDR A/D board =
question
Anyone (Larry?) know if the power LED on the =
A/D board
should blink on/off when the GPS adapter board is sending 1PPS? =
It's been
so long since I looked that I've forgotten.
I've lost my 1PPS somehow and am troubleshooting it. The GPS LED =
is
blinking at 1PPS but I'm not getting it at WinSDR.
Subject: Re: Digest from 02/10/2007 00:01:24
From: Randall Peters PETERS_RD@..........
Date: Mon, 12 Feb 2007 10:13:04 -0500
John,
All too often people want to take the FFT of a full, long record of length T. Of course with most real systems the spectral lines that provide information concerning system dynamics evolve with time. Thus one must use an n-segmented record set of the total, where n = integer to make the most sense of what is happening. The length of each of these n segments is T/n. This total
set of n records comprises the so-called short time Fourier transform (STFT). A common practice is to let the segments be overlapped in time by 50%; i.e., half of the data in an interior segment 1 < i < n being shared with those in segment i+1. The Windaq code Bob has mentioned is really nice for doing the STFT manually (but without overlap), since one can step in time by constant
amounts by simply clicking the left mouse button in the appropriate 'bar' area. With Amaseis, I have been doing the steps by highlighting each of the segmnets sequentially and saving them as a new file. Then later I go back and load these segmented records into Amaseis to read the peak values. For a free-decay, if one plots the dB values versus the shift time, then a straight line
results if the decay is exponential. By doing a trendline fit to this line, one can estimate the Q easily and accurately. The process is described in more detail than most would want in Chapter 21 that I wrote for CRC's "Vibration and Shock Handbook". The Q value is given (Eq. 21-4) by 27.29 times the frequency divided by the absolute value of the slope indicated by the trendline
fit.
About the the PSD. I will be glad to write an Excel file to do the PSD for your AS-1 there in Corvallis--after I get some free time in the hopefully not-too-distant future. Perhaps you would want to post it to your website? If you could send me a known-by-USGS earthquake record readable by Amaseis or WinQuake, that would be a great help.
Randall
>
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 5 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: STFT and PSD
> From: John or Jan Lahr
> Date: Sat, 10 Feb 2007 10:48:31 -0800
>
> Randall,
>
> The STFT sounds useful, but I'm not sure what it is.
>
> Also, could you share your spread sheet for computing the PSD? That
> quantity has always left me scratching my head. Maybe if I played around
> with it a bit, I would be able to appreciate/understand it better.
>
> Thanks,
> John
>
Subject: Re: Digest from 02/11/2007 00:00:50
From: Randall Peters PETERS_RD@..........
Date: Mon, 12 Feb 2007 10:32:00 -0500
Thanks, Roger, for your comments.
I recently told Allan Coleman about the very method you mention (using PrtScrn) to capture graphical information from the monitor. The one change I would recommend--is that folks save (after importing to Paint) the result as a 'gif' rather than a 'bitmap'. The memory requirements of the latter is enormous compared to the compressed former. I have been using this method for well over a decade to generate almost everything that I publish involving graphics. The gif-form can be included directly in LaTex, the software most common for the generation of scientific publications. All that is required is to work with an \includegraphics{} statement in the hybrid code
that I use (one that does Tex to html conversion). I suspect this outstanding software, produced by Mr. Hutchinson
http://hutchinson.belmont.ma.us/tth/
would be free to those of you who might want to use it. Certainly, as an educator, he provided it to me without charge; and I hope he would do the same for amateur seismologists??
Anybody want to check out the details at the indicated 'location'? I would love to see a bumch of us interacting in this way--since graphical information is 'worth (at least) a thousand words". Even if you don't use Tex you can insert the gif's into Word and then save the Word document as an html file. But please, please don't save it as the hated pdf version.
I thoroughly despise pdf documents, and my sentiments must be shared by the Google guys--since their search engine routinely converts pdf stuff to an html form.
If various ones of you want to initiate interchanges with quasi-scientific html pieces like this, I'll bet somebody would be willing to serve as the 'host server' where we may all look at them?? I mentioned to John Lahr the matter of a PSD 'calculator' using Excel, working with data from his AS1. My guess is that we could post PSD's from any of our instruments in a way that even USGS might eventually 'salivate over' (since nobody to my knowledge routinely publishes instrument-independent data for earthquakes).
Randall
psn-l-digest-request@.............. wrote:
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 1 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Exporting FFT data
> From: Roger Sparks
> Date: Sun, 11 Feb 2007 08:14:55 -0800
>
> Good Morning All,
>
> Dr. Randall Peters writes "
>
> To my knowledge, Amaseis does not
> presently allow for saving (exporting) the spectral data, whereas the version of
> WinQuake that I am using does. I don't know if Larry has folded that capability
> into the latest version of the code on his website."
>
> My latest version of WinQuake does not export the data from the FFT analysis but does save the screen containing the output as a "gif" file. It sounds like Dr. Peters could use the data file so that he could further process the data.
>
> Amaseis does not have any provision for recording FFT data or the screen. However, there is a way to accomplish a screen save containing the Amaseis FFT results. We can take advantage of the Windows "print screen" capability.
>
> You will notice that every computer keyboard has a key labeled "Print Screen". When this key is pressed, the contents of the window (no matter what program is running) is saved to memory. Next, find and open the ancient program "Paint" which was included with the "Accessory" programs in all versions of Windows through Windows XP. Look in the "Edit" menu of Paint and you should see that the "Paste" label is active. Click "Paste" and the contents of memory (which should be the screen contents present when "Print Screen" was pressed) should appear in the Paint window. Paint can generate and save a "BMP" file which is a permanent record of the screen display.
>
> Best wishes,
>
> Roger
>
> .
Subject: Re: ASCII file of wave forms and transforms from AmaSeis
From: John or Jan Lahr JohnJan@........
Date: Mon, 12 Feb 2007 10:30:59 -0800
Hi Alan,
Yes, it certainly does help! Thanks for making this change to
AmaSeis. I'll cc the PSN folks, so that they are aware of this new feature.
I put the new executable for AmaSeis
here: http://jclahr.com/science/psn/as1/heli/as1.exe
All one has to do is replace their copy of as1.exe with this one.
Obviously, since the file names are fixed, after extracting an event
or doing an fft, one will need to rename or move the files so that
they will not be overwritten with data from the next event.
Cheers,
John
At 07:54 AM 2/12/2007, you wrote:
>John,
>
>That was easy. Without making any changes to the user interface, I
>now produce the following files:
> * EventData.csv when producing an Event screen.
> * EventFT.csv when doing a linear FFT
> * EventLogFT.csv when doing a log-log FFT
>These can be read into any spreadsheet. Although one I tried that
>had about 85,000 points gave Lotus 1-2-3 heart failure.
>
>Try the attachment and, if you like it, send it to the guy that was
>asking for this.
>
>I found it easy to do this way. If you want the user to have to do
>something to produce the files, it is more work which I don't have
>time for now.
>
>Hope this helps.
>
>Alan
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: ASCII file of wave forms and transforms from AmaSeis
From: Roger Sparks rsparks@..........
Date: Tue, 13 Feb 2007 11:06:13 -0800
Hi John and Alan,
I picked up the new version of Amaseis. It seems to work fine. I can
read the new data files with Quatro Pro. Congratulations on a very
quick development of new feature.
Roger
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Digest from 02/13/2007 00:00:45
From: Randall Peters PETERS_RD@..........
Date: Thu, 15 Feb 2007 08:30:49 -0500
John,
I also updated my Amaseis to permit working with the files. In looking
at a case involving a periodic signal I discovered that the spectral values
of Amaseis are not normalized. The FFT-component magnitudes should not
depend on the time-length of the record, but they are evidently proportional
to that length. My guess is that what is being used is a 'standard'
engineering algorithm (such as employed in Excel) that does not do the
normalization for reason of 'book keeping'.
For those interested in (relative) comparison of spectral intensities in
a given (single) case, the normalization is not important; but to compare
different spectral records, this is required. For the present version of
the code, one must either insure that every case considered is of the same
time duration; or that manual adjustments of a normalizing type be done to
the numbers following their generation. If we are to generate power
spectral densities with the algorithm, I recommend that the code be changed
to give normalized output.
Numerical approximations to the Fourier transform are subtle. The
Cooley-Tukey algorithm which allows the unwieldy discrete version to be
'streamilined' to the fast version is not easily understood and many
examples of normalization confusion exist. The real test of whether one
'got it right' in writing the code is to consider (1) the FFT of a test
case, followed by (2) the inverse FFT to see if the starting 'signal' is
exactly reproduced after doing first the transform and then the inverse
transform. What makes the matter more confusing when it comes to the
development of this type software is that there are six different acceptable
(equivalent) forms of the continuous Fourier transform and its associated
inverse (the math on which the FFT is based). These are all equivalent but
different in appearance according to whether two-pi is put in one place or
the other acceptable place (or split according to the square root) and
according to whether the choice of negative sign in the exponential term is
placed in the direct transform or in the inverse transform. For those who
are interested in the Fourier transform, I have written two papers on the
subject:
(1) Fourier transform construction by vector graphics, AJP 60, 439-441
(1992).
(2) Graphical explanation for the speed of the Fast Fourier Transform,
online at http://arxiv.org/html/math.HO/0302212
Part of our difficulties relate to the following: in physics the
continuous form of the Fourier transform is very common because of its many
theoretical application; the Laplace transform is rarely used. In
electrical engineering, the Laplace transform is very common, but the
continuous Fourier transform is rarely used. Because the FFT derives from
the continuous FT, engineering code has probably therefore been more subject
to the pitfalls that result from non-normalization.
Incidently, the FFT algorithm used by WinQuake is normalized.
Randall
psn-l-digest-request@.............. wrote:
> .------ ------ ------ ------ ------ ------ ------ ------ ------ ------.
> | Message 1 |
> '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
> Subject: Re: ASCII file of wave forms and transforms from AmaSeis
> From: Roger Sparks
> Date: Tue, 13 Feb 2007 11:06:13 -0800
>
> Hi John and Alan,
>
> I picked up the new version of Amaseis. It seems to work fine. I can
> read the new data files with Quatro Pro. Congratulations on a very
> quick development of new feature.
>
> Roger
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-DIGEST-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
Subject: Amaseis
From: "Thomas Dick" dickthomas01@.............
Date: Thu, 15 Feb 2007 09:41:34 -0600
I use Larry's WinSDR and Winquake. Is this program capable of handling his
files? Is it stable windows XP?
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Amaseis Amplitude
From: Gary Falling aviangardens@.......
Date: Thu, 22 Feb 2007 22:11:36 +0000
In the event view of Amaseis, what are the amplitude units. Reading
about Magnitude Calculations it describes the units as counts. Do I
need to convert the counts to microns using the period of my Lehman? Any
references that I might find useful would be appreciated, I am trying to
grasp the total concept.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Seismic Sensors and their Calibration
From: Bobhelenmcclure@.......
Date: Thu, 22 Feb 2007 21:03:53 EST
Hi all,
Dr. John Lahr has placed the subject document on his web site, with my
urging and Dr Wielandt's cooperation. This is a chapter of the new Manual of
Observatory Practice edited by Peter Bormann and Erik Bergmann, and written by
Prof. Erhard Wielandt, Institute of Geophysics, University of Stuttgart.
This document is one every serious amateur should study and have in their
files.
You can view it by going to:
_http://jclahr.com/science/psn/wielandt/man2001.html_
(http://jclahr.com/science/psn/wielandt/man2001.html)
From there, on the first HTML page, there are links to view or download in
MSWord format,
_http://jclahr.com/science/psn/wielandt/NMSOP_06.doc_
(http://jclahr.com/science/psn/wielandt/NMSOP_06.doc)
or to download as a zip file containing all the HTML pages of the document,
_http://jclahr.com/science/psn/wielandt/Seismic%20Sensors.zip_
(http://jclahr.com/science/psn/wielandt/Seismic%20Sensors.zip)
This chapter was written for professional seismographers, but there is
much there for all amateurs as well.
Regards,
Bob
************************************** AOL now offers free
email to everyone. Find out more about what's free from AOL at
http://www.aol.com.
Hi all,
Dr. John Lahr has placed the subject document on his web site, w=
ith=20
my urging and Dr Wielandt's cooperation. This is a chapter of the new Manual=
of=20
Observatory Practice edited by Peter Bormann and Erik Bergmann, and written=20=
by=20
Prof. Erhard Wielandt, Institute of Geophysics, University of Stuttgart.
This document is one every serious amateur should study and h=
ave=20
in their files.
This chapter was written for professional seismographers, but th=
ere=20
is much there for all amateurs as well.
Regards,
Bob
Subject: Update to my web page
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sun, 25 Feb 2007 00:08:58 +0000
Hi all
I have updated my web page with plots from USGS around the world. The
new page can be viewed here.
http://www.simnet.is/jonfr500/earthquake/tremorusgsen.htm
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Test message, new email address
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Sun, 25 Feb 2007 00:16:58 +0000
Hi all
This is just a test email since I was moving the psn postlist
subscripsion to a new email address, the older email is still working
for those who have it, but I am currently fasing it out until the day I
stop using it, problay in two years time or so.
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Greenland sea earthquake swarm
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Mon, 26 Feb 2007 02:18:17 +0000
Hi all
At the moment there is a modarate earthquake swarm ongoing in Greenland
sea, close to 73.30N and 7E. The larest earthquake was mag 5.3 at 21:53
25th feb, 2007. More info this earthquakes
here,http://www.emsc-csem.org/index.php?page=3Dcurrent&sub=3Dlist
Regards.=20
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Earthquake swarm out on Reykjanes Ridge
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Tue, 27 Feb 2007 06:00:29 +0000
Hi all
There has started a earthquake swarm out on the Reykjanes Ridge, with
the largest earthquakes above mag 3.9. The largest earthquakes are
clearly visable on my plot.
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Gain problem
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Tue, 27 Feb 2007 13:32:25 +0000
Hi all
I got new hardware from larry today and I was setting it up. I have
problems setting up the gain for Channel 1 (Z). I don't get it up as hig
as I want. This can be seen on my online plot now, when a earthquake
appears on E-W and N-S, it doesn't appear on Z.
I might be wrong on this, but I don't think that the gain is as hig as I
want it to be. But I won't really know until I get a desent size
earthquake to mesure it with. But I did recored a mag 2.8 (IMO automatic
system tells the that was it's size) and I did see it on all channels,
uncluding Z, but Z only had 110nm top, but n-s had 290nm top and e-w had
410nm top. I want to put the gain settings for all the channels on the
same level. I don't think that is the case at the moment.
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Gain problem
From: ChrisAtUpw@.......
Date: Tue, 27 Feb 2007 11:17:16 EST
In a message dated 2007/02/27, jonfr@......... writes:
> I got new hardware from larry today and I was setting it up. I have
> problems setting up the gain for Channel 1 (Z). I don't get it up as hig
> as I want. This can be seen on my online plot now, when a earthquake
> appears on E-W and N-S, it doesn't appear on Z.
Hi Jon,
There are two gain controls on Larry's boards. Close behind the first
opamp, there are two pins about 1 cm high, 1mm square and they usually have
black plastic shorting clip. For higher gains, this link should be placed on
only one pin so that the circuit is left open. Then there some capacitors and a
vertical potentiometer with an adjustment screw on the top (yellow in photo).
This adjusts the gain from x1 to x10. Then you have a 14 pin DIL opamp and
towards the output of the board a zero set potentiometer.
> Each channel has a two-pin jumper that controls the gain of the first
> op-amp. With the jumper in, the gain of the board will be ~145 to ~1700. This
> range should be used with sensors that have a high output voltage, like a
> geophone. With the jumper removed, the gain range is ~600 to ~6000.
Regards,
Chris Chapman
In a me=
ssage dated 2007/02/27, jonfr@......... writes:
I got new hardware from larry t=
oday and I was setting it up. I have
problems setting up the gain for Channel 1 (Z). I don't get it up as hig
as I want. This can be seen on my online plot now, when a earthquake
appears on E-W and N-S, it doesn't appear on Z.
Hi Jon,
There are two gain controls on Larry's=20=
boards. Close behind the first opamp, there are two pins about 1 cm high, 1m=
m square and they usually have black plastic shorting clip. For higher gains=
, this link should be placed on only one pin so that the circuit is l=
eft open. Then there some capacitors and a vertical potentiometer with an ad=
justment screw on the top (yellow in photo). This adjusts the gain from x1 t=
o x10. Then you have a 14 pin DIL opamp and towards the output of the board=20=
a zero set potentiometer.
Each channel has a two-pin jump=
er that controls the gain of the first op-amp. With the jumper in, the gain=20=
of the board will be ~145 to ~1700. This range should be used with sensors t=
hat have a high output voltage, like a geophone. With the jumper removed, th=
e gain range is ~600 to ~6000.
Regards,
Chris Chapman =20
Subject: 24 Bit Digitizer
From: "Bambang Sunardi" b.sunardi@.........
Date: Wed, 28 Feb 2007 09:12:07 +0700
I wish to develop 24 Bit digitizer to my digital seismograph.
I wish to get electronic scheme to assist me develop 24 bit digitizer.
anyone can help me please?
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: 24 Bit Digitizer
From: "Bambang Sunardi" b.sunardi@.........
Date: Wed, 28 Feb 2007 09:12:07 +0700
I wish to develop 24 Bit digitizer to my digital seismograph.
I wish to get electronic scheme to assist me develop 24 bit digitizer.
anyone can help me please?
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: 24 Bit Digitizer
From: ChrisAtUpw@.......
Date: Tue, 27 Feb 2007 22:55:58 EST
In a message dated 2007/02/28, b.sunardi@......... writes:
> I wish to develop 24 Bit digitizer to my digital seismograph.
> I wish to get electronic scheme to assist me develop 24 bit digitizer.
> anyone can help me please?
Hi there,
Do you want to buy one or to actually make one?
There are at least two suppliers who sell complete 24 bit boards at
'reasonable prices' and software to go with them.
If you make one, how are you going to obtain the software to drive it?
What seismic data recording and analysis program do you plan to use?
An 'ordinary' laboratory ADC recorder program is unlikely to have all the data
extraction, filtering, processing and analysis that seismologists usually
want. Nor is it likely to have the precision timing required. The software clocks
on most computers are hopelessly inaccurate for seismic work.
The design and construction of a 24 bit ADC board is not a 'simple
task', but requires knowledge of the design, skill and the facilities to design
and produce quite a complex printed circuit board.
If you wish to integrate the digtial electronics into the seismometer
control loop, the problem is likely to get quite a lot harder.
Regards,
Chris Chapman
In a me=
ssage dated 2007/02/28, b.sunardi@......... writes:
I wish to develop 24 Bit digiti=
zer to my digital seismograph.
I wish to get electronic scheme to assist me develop 24 bit digitizer.
anyone can help me please?
Hi there,
Do you want to buy one or to actually m=
ake one?
There are at least two suppliers who se=
ll complete 24 bit boards at 'reasonable prices' and software to go with the=
m.
If you make one, how are you going to o=
btain the software to drive it?
What seismic data recording and analysi=
s program do you plan to use? An 'ordinary' laboratory ADC recorder program=20=
is unlikely to have all the data extraction, filtering, processing and analy=
sis that seismologists usually want. Nor is it likely to have the precision=20=
timing required. The software clocks on most computers are hopelessly inaccu=
rate for seismic work.
The design and construction of a 24 bit=
ADC board is not a 'simple task', but requires knowledge of the design, ski=
ll and the facilities to design and produce quite a complex printed circuit=20=
board.
If you wish to integrate the digtial el=
ectronics into the seismometer control loop, the problem is likely to get qu=
ite a lot harder.
Regards,
Chris Chapman =20
Subject: Re: Gain problem
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Wed, 28 Feb 2007 06:20:28 +0000
Hi
Chris, thanks for that. But I already know about the basic settings. My
issue is that I am not sure how I can turn the gain up properly, so I
can have my system more sensitive to earthquakes. Since I don't have
geophones are low gains. I don't know what direction to turn this to get
the gain up, but not to get it too hig and since this turns full circle,
it is hard for me to tell when I am at minimum and when I am at farly
high gain.
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Reykjanes Ridge earthquake swarm
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Wed, 28 Feb 2007 11:01:52 +0000
Hi all
The Reykjanes Ridge earthquake swarm that did happen yesterday appears
to be over, it has been quiet now for almost a 24 hours.=20
In this earthquake swarm IMO did record over 100 earthquakes, the
largest onces where over mag 4 in size. There was also more the a dosen
mag 3 and larger earthquakes. I did record more then 24 earthquakes from
this swarm, most of them where over mag 3 in size. This is a new record
for me in number of earthquakes over a period of one day, problay a
record for earthquakes pr week also.
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Gain problem
From: "Michael Kimzey" mckimzey@...........
Date: Wed, 28 Feb 2007 06:41:14 -0500
Jon,
>I am not sure how I can turn the gain up properly, so I
>can have my system more sensitive to earthquakes. Since I don't have
>geophones are low gains. I don't know what direction to turn this to get
>the gain up, but not to get it too high and since this turns full circle,
>it is hard for me to tell when I am at minimum and when I am at fairly
>high gain.
I had the same questions when I received my board. You can try the
following: take a small screwdriver (a jewelers screwdriver) and set the
pot nearest the jumper to minimum by turning counter-clockwise gently. The
pots are 20-turn, and when you reach the end, you will feel a
click-click-click to know that you reached the end. I then adjusted the
pots up until the max and min were around +100 / -100. This is a very
unscientific way that I did it. I think that Larry has directions for
accurately determining the gain, but I don't have access to the test
equipment required.
While I'm posting - two questions for the group:
1) does anyone know of the status of the Volksmeter. I had heard that maybe
sometime early in 2007 there might be it's debut. Is there a release date?
2) I have been reading about the STM-8 vertical at the site and in the
aggregate emails at PSN. How specific does one have to be with the voice
coil? I can't fine the Radio Shack models. Would any subwoofer work, or
would there be significant electronic modifications needed if one used
another subwoofer?
- Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Gain problem
From: ChrisAtUpw@.......
Date: Wed, 28 Feb 2007 07:06:50 EST
In a message dated 2007/02/28, jonfr@......... writes:
> My issue is that I am not sure how I can turn the gain up properly, so I
> can have my system more sensitive to earthquakes. Since I don't have
> geophones are low gains. I don't know what direction to turn this to get
> the gain up, but not to get it too high and since this turns full circle,
> it is hard for me to tell when I am at minimum and when I am at fairly
> high gain.
Hi Jon,
The pre-set potentiometers may be 10, 15, 18 or 22 turns. If you wind
them continually in one direction, they stiffen up when you reach the end of
the track and any further rotation produces an audible click. This is a safety
mechanism which prevents damage to the mechanism by 'over winding'. You can
then wind them in the opposite direction, counting turns, until you hear another
click - or simply ask Larry what potentiometers he uses?
If you have a digital multimeter with a resistance range, you can
measure / setup the gain. After switching OFF the power, you need to locate the
opamp connected to the gain set potentiometer and note it's -ve input, output
and Earth pins. If you read the type number, say LF412, LM324, LF444 etc and
type this into Google, you should be able to download a data sheet with the pin
connections. Alternatively, go to the manufacturer's website.
You measure the resistance between the -ve inverting input and earth,
say Rb Ohms. You then measure the resistance between the -ve input and the
output, say Ra Ohms. The gain of the stage is then = 1 + Ra/Rb. You can then turn
the set screw on the potentiometer to give the value of the resistance / gain
that you require. Rb will have a fixed value. Ra will have minimum and
maximum values which you can measure after winding the potentiometer to both end
stops. Note the turn direction, clockwise / counter clockwise which increases the
resistance.
Look up http://jclahr.com/science/psn/cochrane/index.html and opamp
U5b. Rb = R9 + R27 = 1 + 2.2 = 3.2 K Ohms. Ra = R26 + R7 = 1 K + (0 to 50) K
Ohms preset. So the minimum gain = 1 + 1/3.2 = 1.31 and the max gain = 1 + 51/3.2
= 16.9 This gives a gain range of 1 to 12.9. Sorry that I don't have Larry's
current circuit.
If you just want to set up equal gains on your three opamps, set the
resistance between the output and the -ve input to be the same on all three.
Hope that this helps?
Regards,
Chris Chapman
In a me=
ssage dated 2007/02/28, jonfr@......... writes:
My issue is that I am not sure=20=
how I can turn the gain up properly, so I
can have my system more sensitive to earthquakes. Since I don't have
geophones are low gains. I don't know what direction to turn this to get
the gain up, but not to get it too high and since this turns full circle,
it is hard for me to tell when I am at minimum and when I am at fairly
high gain.
Hi Jon,
The pre-set potentiometers may be 10, 1=
5, 18 or 22 turns. If you wind them continually in one direction, they stiff=
en up when you reach the end of the track and any further rotation produces=20=
an audible click. This is a safety mechanism which prevents damage to the me=
chanism by 'over winding'. You can then wind them in the opposite direction,=
counting turns, until you hear another click - or simply ask Larry what pot=
entiometers he uses?
If you have a digital multimeter with a=
resistance range, you can measure / setup the gain. After switching O=
FF the power, you need to locate the opamp connected to the gain set potenti=
ometer and note it's -ve input, output and Earth pins. If you read the type=20=
number, say LF412, LM324, LF444 etc and type this into Google, you should be=
able to download a data sheet with the pin connections. Alternatively, go t=
o the manufacturer's website.
You measure the resistance between the=20=
-ve inverting input and earth, say Rb Ohms. You then measure the resistance=20=
between the -ve input and the output, say Ra Ohms. The gain of the stage is=20=
then =3D 1 + Ra/Rb. You can then turn the set screw on the potentiometer to=20=
give the value of the resistance / gain that you require. Rb will have a fix=
ed value. Ra will have minimum and maximum values which you can measure afte=
r winding the potentiometer to both end stops. Note the turn direction, cloc=
kwise / counter clockwise which increases the resistance.
Look up http://jclahr.com/science/psn/c=
ochrane/index.html and opamp U5b. Rb =3D R9 + R27 =3D 1 + 2.2 =3D 3.2 K Ohms=
.. Ra =3D R26 + R7 =3D 1 K + (0 to 50) K Ohms preset. So the minimum gain=20=
=3D 1 + 1/3.2 =3D 1.31 and the max gain =3D 1 + 51/3.2 =3D 16.9 This gives a=
gain range of 1 to 12.9. Sorry that I don't have Larry's current circuit.
If you just want to set up equal gains=20=
on your three opamps, set the resistance between the output and the -ve inpu=
t to be the same on all three.
Hope that this helps?
Regards,
Chris Chapman =20
Subject: Re: Gain problem
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Wed, 28 Feb 2007 12:23:34 +0000
Hi Michael & Chris.
With some trial and error I think I was able to set all the channels for
the geophone at the gain I want. I can at least detect the background
noise. But that is my way to check for that at the moment, since it's
quiet in earthquakes at the moment.
Thanks for the help. But I wish this was more simply done the current
methoud is.
Regards.=20
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: STM-8
From: ChrisAtUpw@.......
Date: Wed, 28 Feb 2007 08:10:33 EST
In a message dated 2007/02/28, mckimzey@........... writes:
> 2) I have been reading about the STM-8 vertical at the site and in the
> aggregate emails at PSN. How specific does one have to be with the voice
> coil? I can't find the Radio Shack models. Would any subwoofer work, or
> would there be significant electronic modifications needed if one used
> another subwoofer?
Hi Mike,
I suspect that many subwoofers could be made to work, but do note that
Sean turned out the polepieces to increase the pole gap and wound his own
feedback coil, which had more turns. The pole gap spacing likely needs to be
increased for seismometer use. The magnet systems chosen were demountable / bolt
together. Many current speaker systems use ferrite magnets firmly glued in
place and have very narrow pole gaps, which could make setup / alignment
difficult.
An alternative is to use a flat rectangular coil with quad NdFeB
magnets on mild steel backing plates. You might find this construction easier? See
drawings at http://jclahr.com/science/psn/chapman/lehman/index.html The more
powerful NdFeB magnets can give larger magnetic fields in a wider gap.
You need to be able to measure the force / current characteristic and
the resistance to calculate the feedback required in a triple loop system.
Look also how Bob McClure has used NdFeB magnet / coil systems at
http://jclahr.com/science/psn/mcclure/index.html
Regards,
Chris Chapman
In a me=
ssage dated 2007/02/28, mckimzey@........... writes:
2) I have been reading about th=
e STM-8 vertical at the site and in the
aggregate emails at PSN. How specific does one have to be with the voi=
ce
coil? I can't find the Radio Shack models. Would any subwoofer w=
ork, or
would there be significant electronic modifications needed if one used
another subwoofer?
Hi Mike,
I suspect that many subwoofers could be=
made to work, but do note that Sean turned out the polepieces to increas=
e the pole gap and wound his own feedback coil, which had more turns. Th=
e pole gap spacing likely needs to be increased for seismometer use. The mag=
net systems chosen were demountable / bolt together. Many current spe=
aker systems use ferrite magnets firmly glued in place and have very narrow=20=
pole gaps, which could make setup / alignment difficult.
An alternative is to use a flat rectang=
ular coil with quad NdFeB magnets on mild steel backing plates. You might fi=
nd this construction easier? See drawings at http://jclahr.com/science/psn/c=
hapman/lehman/index.html The more powerful NdFeB magnets can give larger mag=
netic fields in a wider gap.
You need to be able to measure the forc=
e / current characteristic and the resistance to calculate the feedback requ=
ired in a triple loop system.
Look also how Bob McClure has used NdFe=
B magnet / coil systems at http://jclahr.com/science/psn/mcclure/index.html<=
BR>
Regards,
Chris Chapman =20
Subject: psn file issue
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Wed, 28 Feb 2007 16:54:20 +0000
Hi all
I am having a bit if a psn file issue at the moment. The problem is
because of the earthquake swarm that did happen yesterday and how it was
recored by my system. Many of the earthquakes that I did record are less
then 1 min apart in the trace, so when I plot them I end up with the
same file time as the first earthquake. The problem is the start time, I
can rename the files so they mark 070227.131420.hvt1e.psn, but when I
try to send them to psn event file list, I get this and that is the main
problem, 070227.131420.hvt1e \quakes\0702\070227.131400.hvt1e.psn
Upload OK. This also creates problem with winquake, since it reads the
same info.
Is it possible for me to change the start time of the files, so I can
have it as close as possible for the orgin of the earthquake.
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: STM-8
From: "Keith Payea" kpayea@...........
Date: Wed, 28 Feb 2007 08:54:52 -0800
As Chris suggests, the gap is the part that is hardest to work around. This
varies a lot from woofer to woofer. My experience has been that a high
power but very cheap unit will have the biggest gap. Expensive woofers have
small gaps for better performance, at high power they do this with exotic
voice coil designs. I got lucky with a woofer given to me by a friend
because it had a rip in the cone. It turned out to have a gap big enough to
work with. I did spend some time with a Dremel tool opening the entry area
to the gap. In the seismometer, the coil moves through a slight arc, so a
little extra clearance is needed there.
The electrical performance of woofers doesn't vary that much, and the "gain"
or generator constant is easily measured and compensated. Much easier than
trying to get bits of metal filings out of the magnet gap!
I have some pictures of my version at:
http://www.bryantlabs.net/VertSeis.html
Good Luck!
Keith
Keith Payea
Bryant Labs
kpayea@..............
www.bryantlabs.net
(707) 566-8935
_____
From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of ChrisAtUpw@.......
Sent: Wednesday, February 28, 2007 5:11 AM
To: psn-l@..............
Subject: Re: STM-8
In a message dated 2007/02/28, mckimzey@........... writes:
2) I have been reading about the STM-8 vertical at the site and in the
aggregate emails at PSN. How specific does one have to be with the voice
coil? I can't find the Radio Shack models. Would any subwoofer work, or
would there be significant electronic modifications needed if one used
another subwoofer?
Hi Mike,
I suspect that many subwoofers could be made to work, but do note
that Sean turned out the polepieces to increase the pole gap and wound his
own feedback coil, which had more turns. The pole gap spacing likely needs
to be increased for seismometer use. The magnet systems chosen were
demountable / bolt together. Many current speaker systems use ferrite
magnets firmly glued in place and have very narrow pole gaps, which could
make setup / alignment difficult.
An alternative is to use a flat rectangular coil with quad NdFeB
magnets on mild steel backing plates. You might find this construction
easier? See drawings at
http://jclahr.com/science/psn/chapman/lehman/index.html The more powerful
NdFeB magnets can give larger magnetic fields in a wider gap.
You need to be able to measure the force / current characteristic and
the resistance to calculate the feedback required in a triple loop system.
Look also how Bob McClure has used NdFeB magnet / coil systems at
http://jclahr.com/science/psn/mcclure/index.html
Regards,
Chris Chapman
As Chris=20
suggests, the gap is the part that is hardest to work =
around. =20
This varies a lot from woofer to woofer. My experience has been =
that a=20
high power but very cheap unit will have the biggest gap. =
Expensive=20
woofers have small gaps for better performance, at high power they do =
this with=20
exotic voice coil designs. I got lucky with a woofer given to =
me by a=20
friend because it had a rip in the cone. It turned out to =
have a gap=20
big enough to work with. I did spend some time with a Dremel=20
tool opening the entry area to the gap. In the =
seismometer,=20
the coil moves through a slight arc, so a little extra clearance is =
needed=20
there.
The electrical=20
performance of woofers doesn't vary that much, and the =
"gain" or=20
generator constant is easily measured and compensated. Much =
easier=20
than trying to get bits of metal filings out of the magnet=20
gap!
I =
have some=20
pictures of my version at: http://www.bryantlabs.ne=
t/VertSeis.html
Good=20
Luck!
Keith
Keith=20
Payea
Bryant Labs
kpayea@..............
www.bryantlabs.net
(707)=20
566-8935
From: psn-l-request@.................
[mailto:psn-l-request@............... On Behalf Of=20
ChrisAtUpw@....... Sent: Wednesday, February 28, 2007 5:11 =
AM To: psn-l@.............. Subject: Re:=20
STM-8
In =
a message=20
dated 2007/02/28, mckimzey@........... writes:
2) I have been reading about the STM-8 vertical at the =
site and in=20
the aggregate emails at PSN. How specific does one have to =
be with=20
the voice coil? I can't find the Radio Shack models. =
Would any=20
subwoofer work, or would there be significant electronic =
modifications=20
needed if one used another subwoofer?
Hi=20
Mike,
I suspect that many =
subwoofers=20
could be made to work, but do note that Sean turned out the =
polepieces to=20
increase the pole gap and wound his own feedback coil, which had =
more turns.=20
The pole gap spacing likely needs to be increased for seismometer use. =
The=20
magnet systems chosen were demountable / bolt together. Many =
current=20
speaker systems use ferrite magnets firmly glued in place and have very =
narrow=20
pole gaps, which could make setup / alignment=20
difficult. An alternative is to =
use a=20
flat rectangular coil with quad NdFeB magnets on mild steel backing =
plates. You=20
might find this construction easier? See drawings at=20
http://jclahr.com/science/psn/chapman/lehman/index.html The more =
powerful NdFeB=20
magnets can give larger magnetic fields in a wider=20
gap. You need to be able to =
measure the=20
force / current characteristic and the resistance to calculate the =
feedback=20
required in a triple loop =
system. Look=20
also how Bob McClure has used NdFeB magnet / coil systems at=20
http://jclahr.com/science/psn/mcclure/index.html &nb=
sp; =20
=20
Regards,
Chris =
Chapman=20
Subject: Re: STM-8
From: ChrisAtUpw@.......
Date: Wed, 28 Feb 2007 12:57:45 EST
In a message dated 2007/02/28, kpayea@........... writes:
> Much easier than trying to get bits of metal filings out of the magnet gap!
Hi Keith,
First off, 'wipe' the inside of the gap with a round mild steel rod
several times. This will pick up most of the filings. Then you press on and peel
off strips of Gaffer Tape, using a wood spatula. This has a rubber based
adhesive which is good at picking up and removing dust, dirt and magnetic
particles.
Regards,
Chris Chapman
In a me=
ssage dated 2007/02/28, kpayea@........... writes:
Much easier than trying to get=
bits of metal filings out of the magnet gap!
Hi Keith,
First off, 'wipe' the inside of the gap=
with a round mild steel rod several times. This will pick up most of the fi=
lings. Then you press on and peel off strips of Gaffer Tape, using a wood sp=
atula. This has a rubber based adhesive which is good at picking up and remo=
ving dust, dirt and magnetic particles.
Regards,
Chris Chapman =20
Subject: Re: STM-8
From: "Michael Kimzey" mckimzey@...........
Date: Wed, 28 Feb 2007 21:40:39 -0500
Hi Chris (and everyone else, too...)
You wrote:
> An alternative is to use a flat rectangular coil with quad NdFeB
>magnets on mild steel backing plates. You might find this construction
>easier? See
>drawings at http://jclahr.com/science/psn/chapman/lehman/index.html The
>more
>powerful NdFeB magnets can give larger magnetic fields in a wider gap.
I built a damping assembly for my AS1-copy and used this type of dampening.
(excellent drawings!) For it's use here, I guess I would use a coil (maybe
like a 220v relay coil?) between the magnets and instead of using it as the
actual sensor (like on the AS1), it would rather function only as a
damper...do I understand correct?
> You need to be able to measure the force / current characteristic
>and
>the resistance to calculate the feedback required in a triple loop system.
> Look also how Bob McClure has used NdFeB magnet / coil systems at
>http://jclahr.com/science/psn/mcclure/index.html
It is this part that scares me. I don't have a really good backround in
electronic theory to understand some of the fine points of this stuff. If I
went ahead with this some time in the future, are there instructions
somewhare that could tell me how to measure and calculate these values? I
know that in reading though STM's emails that there is mathlab formula's and
other such stuff....but I don't even know what mathlab IS! :(
- Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: STM-8
From: ChrisAtUpw@.......
Date: Wed, 28 Feb 2007 23:39:48 EST
In a message dated 2007/03/01, mckimzey@........... writes:
> You wrote:
> > An alternative is to use a flat rectangular coil with quad NdFeB
> >magnets on mild steel backing plates. You might find this construction
> >easier? See
> >drawings at http://jclahr.com/science/psn/chapman/lehman/index.html The
> >more
> >powerful NdFeB magnets can give larger magnetic fields in a wider gap.
>
> I built a damping assembly for my AS1-copy and used this type of dampening.
> For it's use here, I guess I would use a coil (maybe
> like a 220v relay coil?) between the magnets and instead of using it as the
>
> actual sensor (like on the AS1), it would rather function only as a
> damper...do I understand correct?
Hi Mike,
That is not totally correct.
For a STM-8 you need a active force feedback coil. Placing a flat coil
in the central high field position and putting a current through it allows
you to generate a linear force / current relationship parallel to the magnet
faces. But you are much better off using a thin rectangular former and a fairly
narrow magnet gap, rather than a round relay coil. Make the former using fairly
thin sheet metal with a radial slot + PCB which overlaps the ends of the
joint in the magnets. If you are putting much current through the coil, you will
likely need to cool it. There is a plan of a suitable sensor coil somewhere in
my diagrams, but for force feedback you want thicker wire and a resistance of
maybe 100 Ohms or less. If you try to use a high impedance / high inductance
sensor type coil, you are likely to have problems making the circuit stable. I
seem to remember that coil systems and forces were discussed, but using
speaker magnets and cylindrical coils.
> > You need to be able to measure the force / current characteristic
> and
> >the resistance to calculate the feedback required in a triple loop system.
>
> It is this part that scares me. I don't have a really good backround in
> electronic theory to understand some of the fine points of this stuff. If I
> went ahead with this some time in the future, are there instructions
> somewhare that could tell me how to measure and calculate these values? I
> know that in reading though STM's emails that there is mathlab formula's and
>
> other such stuff....but I don't even know what mathlab IS!
Matlab is a fairly large and complicated mathematics spreadsheet software
program. It is fairly old now, but I have not used it. It allows you to plot
graphical system responses.
You need a multimeter, a power supply and a wirewound variable
resistor. You weigh the coil + former, suspend it freely in the centre of the magnet
assembly and put enough DC current through it to take it's own weight. You
measure the current and the coil resistance with the multimeter. I have some
small electronic digital pocket scales which allow me to measure to 0.1 gm. Do you
have access to a chemical lab balance / know anyone who has? You don't need
1% precision!
Regards,
Chris Chapman
In a me=
ssage dated 2007/03/01, mckimzey@........... writes:
You wrote:
> An alternative is to use a fl=
at rectangular coil with quad NdFeB
>magnets on mild steel backing plates. You might find this construction <=
BR>
>easier? See
>drawings at http://jclahr.com/science/psn/chapman/lehman/index.html The=20=
>more
>powerful NdFeB magnets can give larger magnetic fields in a wider gap.
I built a damping assembly for my AS1-copy and used this type of dampening.=20=
For it's use here, I guess I would use a coil (maybe
like a 220v relay coil?) between the magnets and instead of using it a=
s the
actual sensor (like on the AS1), it would rather function only as a
damper...do I understand correct?
Hi Mike,
That is not totally correct.
For a STM-8 you need a active force fee=
dback coil. Placing a flat coil in the central high field position and putti=
ng a current through it allows you to generate a linear force / current rela=
tionship parallel to the magnet faces. But you are much better off using a t=
hin rectangular former and a fairly narrow magnet gap, rather than a round r=
elay coil. Make the former using fairly thin sheet metal with a radial slot=20=
+ PCB which overlaps the ends of the joint in the magnets. If you are puttin=
g much current through the coil, you will likely need to cool it. There is a=
plan of a suitable sensor coil somewhere in my diagrams, but for force feed=
back you want thicker wire and a resistance of maybe 100 Ohms or less. If yo=
u try to use a high impedance / high inductance sensor type coil, you are li=
kely to have problems making the circuit stable. I seem to remember that coi=
l systems and forces were discussed, but using speaker magnets and cylindric=
al coils.
> &nb=
sp; You need to be able to measure the force / current character=
istic and
>the resistance to calculate the feedback required in a triple loop syste=
m.
It is this part that scares me. I don't have a really good backround in
electronic theory to understand some of the fine points of this stuff. If I=20=
went ahead with this some time in the future, are there instructions
somewhare that could tell me how to measure and calculate these values? =
; I
know that in reading though STM's emails that there is mathlab formula's and=
other such stuff....but I don't even know what mathlab IS!
Matlab is a fairly large and complicated mathematics spre=
adsheet software program. It is fairly old now, but I have not used it. It a=
llows you to plot graphical system responses.
You need a multimeter, a power supply a=
nd a wirewound variable resistor. You weigh the coil + former, suspend it fr=
eely in the centre of the magnet assembly and put enough DC current through=20=
it to take it's own weight. You measure the current and the coil resistance=20=
with the multimeter. I have some small electronic digital pocket scales whic=
h allow me to measure to 0.1 gm. Do you have access to a chemical lab balanc=
e / know anyone who has? You don't need 1% precision!
Regards,
Chris Chapman =20
Subject: Interesting Article On Seismology
From: "Bob Hancock" carpediem1@.........
Date: Sun, 4 Mar 2007 16:48:23 -0700
http://www.sciencedaily.com/releases/2007/02/070228170312.htm
Subject: Getting started...
From: "Kareem at Heyjoojoo" system98765@.............
Date: Mon, 5 Mar 2007 07:12:49 -0800
Hello all,
I've been using an analog seismograph system (Kinemetrics PS2 with short L4
period sensor) for 5 years now and considering moving to a digital system. I
do have some tools but I'm not sure if I have all that's needed to move to a
digital seismograph system. And I'm not exactly sure how to get started
setting it up. I have one of those DataQ devices with the serial connector,
a small geophone (used by military), and no software yet.
I would like to start using a PC to monitor seismic activity. Where/how
should I start?
Yours truly,
Kareem
1 block from Hayward Fault (northern segment)
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Getting started...
From: ChrisAtUpw@.......
Date: Mon, 5 Mar 2007 11:23:40 EST
In a message dated 2007/03/05, system98765@............. writes:
> I have one of those DataQ devices with the serial connector,
> a small geophone (used by military)
Hi Kareem,
Which Dataq ADC? Some are worse than others. 12 bit is absolute
minimum for seismometers.
Do check, but military geophones were mostly higher frequency, 10 Hz+.
You want a 4.5 Hz or less.
How about constructing a Lehman?
Regards,
Chris Chapman
In a me=
ssage dated 2007/03/05, system98765@............. writes:
I have one of those DataQ devi=
ces with the serial connector,
a small geophone (used by military)
Hi Kareem,
Which Dataq ADC? Some are worse than ot=
hers. 12 bit is absolute minimum for seismometers.
Do check, but military geophones were m=
ostly higher frequency, 10 Hz+. You want a 4.5 Hz or less.
How about constructing a Lehman?
Regards,
Chris Chapman
=20
Subject: Re: Getting started...
From: "tchannel" tchannel@..............
Date: Mon, 5 Mar 2007 13:39:46 -0700
Hi Kareem, I have built five different sensors. Presently using the best
two, one Lehman and one Vertical Spring.
I also am using a computer, AmaSeis, Winquake software, The DataQ194 a/d
converter and Larry's Amp/Filter board. Very happy with all these
components. Email me, if you wish and I can send pictures and Dimensions.
Ted
----- Original Message -----
From: "Kareem at Heyjoojoo"
To: "PSN"
Sent: Monday, March 05, 2007 8:12 AM
Subject: Getting started...
> Hello all,
>
> I've been using an analog seismograph system (Kinemetrics PS2 with short
> L4
> period sensor) for 5 years now and considering moving to a digital system.
> I
> do have some tools but I'm not sure if I have all that's needed to move to
> a
> digital seismograph system. And I'm not exactly sure how to get started
> setting it up. I have one of those DataQ devices with the serial
> connector,
> a small geophone (used by military), and no software yet.
>
> I would like to start using a PC to monitor seismic activity. Where/how
> should I start?
>
> Yours truly,
> Kareem
>
> 1 block from Hayward Fault (northern segment)
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: Getting started...
From: "Kareem at Heyjoojoo" system98765@.............
Date: Mon, 5 Mar 2007 15:47:30 -0800
Hi Chris,
The DAtaQ I have is the model DI-154RS. I bought some years ago...
Kareem
_____
From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of ChrisAtUpw@.......
Sent: Monday, March 05, 2007 8:24 AM
To: psn-l@..............
Subject: Re: Getting started...
In a message dated 2007/03/05, system98765@............. writes:
I have one of those DataQ devices with the serial connector,
a small geophone (used by military)
Hi Kareem,
Which Dataq ADC? Some are worse than others. 12 bit is absolute
minimum for seismometers.
Do check, but military geophones were mostly higher frequency, 10
Hz+. You want a 4.5 Hz or less.
How about constructing a Lehman?
Regards,
Chris Chapman
Hi Chris,
The DAtaQ I have is the model DI-154RS. I =
bought some years=20
ago...
Kareem
From: psn-l-request@.................
[mailto:psn-l-request@............... On Behalf Of=20
ChrisAtUpw@....... Sent: Monday, March 05, 2007 8:24=20
AM To: psn-l@.............. Subject: Re: Getting=20
started...
In =
a message=20
dated 2007/03/05, system98765@............. writes:
I have one of those DataQ devices with the serial =
connector, a=20
small geophone (used by military)
Hi=20
Kareem,
Which Dataq ADC? =
Some are=20
worse than others. 12 bit is absolute minimum for seismometers.=20
Do check, but military =
geophones=20
were mostly higher frequency, 10 Hz+. You want a 4.5 Hz or=20
less.
How about constructing =
a=20
Lehman?
=20
Regards,
Chris=20
Chapman
=
Subject: Re: Getting started...
From: ChrisAtUpw@.......
Date: Tue, 6 Mar 2007 01:28:12 EST
In a message dated 2007/03/05, system98765@............. writes:
> The Dataq I have is the model DI-154RS. I bought some years ago...
> Kareem
Hi Kareem,
That will be OK. It gives 12 bit resolution for a +/-10V input.
You need a sensor, a seismic amplifier/filter, the ADC, a suitable
power supply, a data recording and analysis program, a computer to record and
analyse the signals and a time check system. The computer may need a modem to
download programs, do time checks, send and receive sample data etc.
The time check system may be an on-line timing signal, radio or GPS.
This is the 'unexpected extra'. The software clocks on modern computers cannot
be relied upon to within 30 sec per day! This is hopelessly inaccurate for
seismic recording, when a P wave has a velocity of about 8 km/sec. A 30 sec time
error may give over 150 miles error in the epicentre position. You need to
know the time correct to about a second.
It is not too difficult to make a Lehman using electromagnetic damping
and piano wire, or ball on a plane, or crossed cylinder type suspensions.
This should allow you to set the period to over 20 sec fairly easily - many of
the surface waves are about this period. It is a 'good idea' to make a really
rigid cross braced T type frame to support ALL the components INCLUDING the
damper and the sensor magnets. Make the arm and mass out of non magnetic materials
and put the sense and damper magnets on the base frame. You set up the arm,
sensor and damper alignment first and then set the cross balance and period
using three levelling screws on the frame.
See http://www.jclahr.com/science/psn/chapman/school/MKII/index.html
for a general layout. This seismometer was made in a machine shop. It uses a SS
ball on a carbide plane and a wire suspension. The brass mass is at the end
of the arm, then comes the quad sense magnet and the white pickup coil, then
the suspension block and then the damping plate + the quad sliding magnet. The
sense arm is about 2 ft long, the base about 2 ft 6 in and the frame height
about 1 ft 6 in. I use 3" x 1" x 1/8" thick U Channel Al, large 8" triangular x
3/16" thick bolt on Al corner plates and 1/4" SS bolts.
{Point and knife edge suspensions may severely limit the period and
are not likely to be satisfactory long term. Oil damping is strongly temperature
dependant and messy. Oil 'creeps' slowly over most surfaces and then attracts
dust. Systems which use separate mounting/damping/sensing components may be
much more difficult to set up and to adjust. You really don't need these sort
of problems.}
You will also need a thermally insulating, completely draft proof
'inverted box' type cover. See http://pages.prodigy.net/fxc/seiscoverslg.jpg It
is quite large! I use 2" Celotex with the joints taped and glued with
polyurethane foam grouting, both from building supplies. You can make two layer viewing
windows out of clear mylar transparency copying film or cellophane sheet. If
you don't make a screening box, you will get a lot of 'noise' due to air
turbulence moving the arm. You will probably need a small heater, maybe 10 to 20
Watts inside the top of this housing to prevent air convection noise in the late
evening / early morning.
It is up to you whether you buy or can make the amplifier/filter. You
can buy +/-12V stabilised power supplies fairly cheaply. If you buy Larry's
amplifiers, he will supply an inexpensive wall plug transformer to drive them -
the supply regulators are built into his boards.
NOTE: A large seismometer setup can damage your wealth!
Check your wallet out first? Hope that this helps!
Chris Chapman
In a me=
ssage dated 2007/03/05, system98765@............. writes:
The Dataq I have is the model=20=
DI-154RS. I bought some years ago...
Kareem
Hi Kareem,
That will be OK. It gives 12 bit resolu=
tion for a +/-10V input.
You need a sensor, a seismic amplifier/=
filter, the ADC, a suitable power supply, a data recording and analysis prog=
ram, a computer to record and analyse the signals and a time check system. T=
he computer may need a modem to download programs, do time checks, send and=20=
receive sample data etc.
The time check system may be an on-line=
timing signal, radio or GPS. This is the 'unexpected extra'. The sof=
tware clocks on modern computers cannot be relied upon to within 30 sec per=20=
day! This is hopelessly inaccurate for seismic recording, when a P wave has=20=
a velocity of about 8 km/sec. A 30 sec time error may give over 150 miles er=
ror in the epicentre position. You need to know the time correct to about a=20=
second.
It is not too difficult to make a Lehma=
n using electromagnetic damping and piano wire, or ball on a plane, or cross=
ed cylinder type suspensions. This should allow you to set the period to ove=
r 20 sec fairly easily - many of the surface waves are about this period. It=
is a 'good idea' to make a really rigid cross braced T type frame to suppor=
t ALL the components INCLUDING the damper and the sensor magnets. Make the a=
rm and mass out of non magnetic materials and put the sense and damper magne=
ts on the base frame. You set up the arm, sensor and damper alignment first=20=
and then set the cross balance and period using three levelling screws on th=
e frame.
See http://www.jclahr.com/science/psn/c=
hapman/school/MKII/index.html for a general layout. This seismometer was mad=
e in a machine shop. It uses a SS ball on a carbide plane and a wire suspens=
ion. The brass mass is at the end of the arm, then comes the quad sense magn=
et and the white pickup coil, then the suspension block and then the damping=
plate + the quad sliding magnet. The sense arm is about 2 ft long, the base=
about 2 ft 6 in and the frame height about 1 ft 6 in. I use 3" x 1" x 1/8"=20=
thick U Channel Al, large 8" triangular x 3/16" thick bolt on Al corner plat=
es and 1/4" SS bolts.
{Point and knife edge suspensions may s=
everely limit the period and are not likely to be satisfactory long term. Oi=
l damping is strongly temperature dependant and messy. Oil 'creeps' slowly o=
ver most surfaces and then attracts dust. Systems which use separate mountin=
g/damping/sensing components may be much more difficult to set up and to adj=
ust. You really don't need these sort of problems.}
You will also need a thermally insulati=
ng, completely draft proof 'inverted box' type cover. See http://pages.prodi=
gy.net/fxc/seiscoverslg.jpg It is quite large! I use 2" Celotex with t=
he joints taped and glued with polyurethane foam grouting, both from buildin=
g supplies. You can make two layer viewing windows out of clear mylar transp=
arency copying film or cellophane sheet. If you don't make a screening box,=20=
you will get a lot of 'noise' due to air turbulence moving the arm. You will=
probably need a small heater, maybe 10 to 20 Watts inside the top of this h=
ousing to prevent air convection noise in the late evening / early morning.<=
BR>
It is up to you whether you buy or can=20=
make the amplifier/filter. You can buy +/-12V stabilised power supplies fair=
ly cheaply. If you buy Larry's amplifiers, he will supply an inexpensive wal=
l plug transformer to drive them - the supply regulators are built into his=20=
boards.
NOTE: A large seismometer setup can dam=
age your wealth!
Check your wallet out first? Hope that=20=
this helps!
Chris Chapman =20
Subject: Explosion in =?ISO-8859-1?Q?Nov=E1ky?= - Slovakia
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Tue, 06 Mar 2007 20:28:25 +0000
Hi all
On the 2nd March 2007 there was a large explosion in Slovakia, a town
called Nov=E1ky. The explosion was so big that did record as mag 2.2
earthquake.
More info on this and with pictures can be seen here.
http://www.emsc-csem.org/index.php?page=3Dcurrent&sub=3Drecent&evt=3D200703=
02_EXPLOSION
Regards.
--=20
J=F3n Fr=EDmann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: Getting started...
From: "Kareem at Heyjoojoo" system98765@.............
Date: Tue, 6 Mar 2007 20:16:39 -0800
Hey Chris,
Thanks a million. That's a lot. My space is so limited hence the PS2 system
I've kept. Hmmm... I'll take a look the general layout at the link you
provided.
I'll let you know if I have any further questions.
- KAreem
_____
From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of ChrisAtUpw@.......
Sent: Monday, March 05, 2007 10:28 PM
To: psn-l@..............
Subject: Re: Getting started...
In a message dated 2007/03/05, system98765@............. writes:
The Dataq I have is the model DI-154RS. I bought some years ago...
Kareem
Hi Kareem,
That will be OK. It gives 12 bit resolution for a +/-10V input.
You need a sensor, a seismic amplifier/filter, the ADC, a suitable
power supply, a data recording and analysis program, a computer to record
and analyse the signals and a time check system. The computer may need a
modem to download programs, do time checks, send and receive sample data
etc.
The time check system may be an on-line timing signal, radio or GPS.
This is the 'unexpected extra'. The software clocks on modern computers
cannot be relied upon to within 30 sec per day! This is hopelessly
inaccurate for seismic recording, when a P wave has a velocity of about 8
km/sec. A 30 sec time error may give over 150 miles error in the epicentre
position. You need to know the time correct to about a second.
It is not too difficult to make a Lehman using electromagnetic
damping and piano wire, or ball on a plane, or crossed cylinder type
suspensions. This should allow you to set the period to over 20 sec fairly
easily - many of the surface waves are about this period. It is a 'good
idea' to make a really rigid cross braced T type frame to support ALL the
components INCLUDING the damper and the sensor magnets. Make the arm and
mass out of non magnetic materials and put the sense and damper magnets on
the base frame. You set up the arm, sensor and damper alignment first and
then set the cross balance and period using three levelling screws on the
frame.
See http://www.jclahr.com/science/psn/chapman/school/MKII/index.html
for a general layout. This seismometer was made in a machine shop. It uses a
SS ball on a carbide plane and a wire suspension. The brass mass is at the
end of the arm, then comes the quad sense magnet and the white pickup coil,
then the suspension block and then the damping plate + the quad sliding
magnet. The sense arm is about 2 ft long, the base about 2 ft 6 in and the
frame height about 1 ft 6 in. I use 3" x 1" x 1/8" thick U Channel Al, large
8" triangular x 3/16" thick bolt on Al corner plates and 1/4" SS bolts.
{Point and knife edge suspensions may severely limit the period and
are not likely to be satisfactory long term. Oil damping is strongly
temperature dependant and messy. Oil 'creeps' slowly over most surfaces and
then attracts dust. Systems which use separate mounting/damping/sensing
components may be much more difficult to set up and to adjust. You really
don't need these sort of problems.}
You will also need a thermally insulating, completely draft proof
'inverted box' type cover. See http://pages.prodigy.net/fxc/seiscoverslg.jpg
It is quite large! I use 2" Celotex with the joints taped and glued with
polyurethane foam grouting, both from building supplies. You can make two
layer viewing windows out of clear mylar transparency copying film or
cellophane sheet. If you don't make a screening box, you will get a lot of
'noise' due to air turbulence moving the arm. You will probably need a small
heater, maybe 10 to 20 Watts inside the top of this housing to prevent air
convection noise in the late evening / early morning.
It is up to you whether you buy or can make the amplifier/filter. You
can buy +/-12V stabilised power supplies fairly cheaply. If you buy Larry's
amplifiers, he will supply an inexpensive wall plug transformer to drive
them - the supply regulators are built into his boards.
NOTE: A large seismometer setup can damage your wealth!
Check your wallet out first? Hope that this helps!
Chris Chapman
Hey Chris,
Thanks a million. That's a lot. My space is so =
limited=20
hence the PS2 system I've kept. Hmmm... I'll take a look the =
general=20
layout at the link you provided.
I'll let you know if I have =
any further=20
questions.
- KAreem
From: psn-l-request@.................
[mailto:psn-l-request@............... On Behalf Of=20
ChrisAtUpw@....... Sent: Monday, March 05, 2007 10:28=20
PM To: psn-l@.............. Subject: Re: Getting=20
started...
In =
a message=20
dated 2007/03/05, system98765@............. writes:
The Dataq I have is the model DI-154RS. I bought some =
years=20
ago... Kareem
Hi=20
Kareem,
That will be OK. It =
gives 12=20
bit resolution for a +/-10V =
input. You=20
need a sensor, a seismic amplifier/filter, the ADC, a suitable power =
supply, a=20
data recording and analysis program, a computer to record and analyse =
the=20
signals and a time check system. The computer may need a modem to =
download=20
programs, do time checks, send and receive sample data=20
etc. The time check system may =
be an=20
on-line timing signal, radio or GPS. This is the 'unexpected =
extra'. The=20
software clocks on modern computers cannot be relied upon to within 30 =
sec per=20
day! This is hopelessly inaccurate for seismic recording, when a P wave =
has a=20
velocity of about 8 km/sec. A 30 sec time error may give over 150 miles =
error in=20
the epicentre position. You need to know the time correct to about a=20
second. It is not too difficult =
to make=20
a Lehman using electromagnetic damping and piano wire, or ball on a =
plane, or=20
crossed cylinder type suspensions. This should allow you to set the =
period to=20
over 20 sec fairly easily - many of the surface waves are about this =
period. It=20
is a 'good idea' to make a really rigid cross braced T type frame to =
support ALL=20
the components INCLUDING the damper and the sensor magnets. Make the arm =
and=20
mass out of non magnetic materials and put the sense and damper magnets =
on the=20
base frame. You set up the arm, sensor and damper alignment first and =
then set=20
the cross balance and period using three levelling screws on the=20
frame. See=20
http://www.jclahr.com/science/psn/chapman/school/MKII/index.html for a =
general=20
layout. This seismometer was made in a machine shop. It uses a SS ball =
on a=20
carbide plane and a wire suspension. The brass mass is at the end of the =
arm,=20
then comes the quad sense magnet and the white pickup coil, then the =
suspension=20
block and then the damping plate + the quad sliding magnet. The sense =
arm is=20
about 2 ft long, the base about 2 ft 6 in and the frame height about 1 =
ft 6 in.=20
I use 3" x 1" x 1/8" thick U Channel Al, large 8" triangular x 3/16" =
thick bolt=20
on Al corner plates and 1/4" SS bolts. =
=20
{Point and knife edge suspensions may severely limit the period and are =
not=20
likely to be satisfactory long term. Oil damping is strongly temperature =
dependant and messy. Oil 'creeps' slowly over most surfaces and then =
attracts=20
dust. Systems which use separate mounting/damping/sensing components may =
be much=20
more difficult to set up and to adjust. You really don't need these sort =
of=20
problems.} You will also need a=20
thermally insulating, completely draft proof 'inverted box' type cover. =
See=20
http://pages.prodigy.net/fxc/seiscoverslg.jpg It is quite large! I =
use 2"=20
Celotex with the joints taped and glued with polyurethane foam grouting, =
both=20
from building supplies. You can make two layer viewing windows out of =
clear=20
mylar transparency copying film or cellophane sheet. If you don't make a =
screening box, you will get a lot of 'noise' due to air turbulence =
moving the=20
arm. You will probably need a small heater, maybe 10 to 20 Watts inside =
the top=20
of this housing to prevent air convection noise in the late evening / =
early=20
morning. It is up to you whether =
you buy=20
or can make the amplifier/filter. You can buy +/-12V stabilised power =
supplies=20
fairly cheaply. If you buy Larry's amplifiers, he will supply an =
inexpensive=20
wall plug transformer to drive them - the supply regulators are built =
into his=20
boards.
NOTE: A large =
seismometer=20
setup can damage your wealth! =
Check your=20
wallet out first? Hope that this=20
helps!
Chris Chapman=20
Subject: Has http://quake.wr.usgs.gov/ been hacked?
From: "Stephen Hammond" shammon1@.............
Date: Mon, 12 Mar 2007 12:09:28 -0700
I think this link has been hacked. http://quake.wr.usgs.gov/ It should
be the local California seismic activity. I get a porn site when I click
on the link and I also get a panel that says the link is no longer
valid. Are others seeing the same thing?
Thanks, Steve Hammond
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
From: "Jerry Payton" gpayton880@.......
Date: Mon, 12 Mar 2007 14:16:49 -0500
Looks OK & normal here.
Best Regards,
Gerald Payton
----- Original Message -----
From: Stephen Hammond
To: psn-l@..............
Sent: Monday, March 12, 2007 2:09 PM
Subject: Has http://quake.wr.usgs.gov/ been hacked?
I think this link has been hacked. http://quake.wr.usgs.gov/ It should
be the local California seismic activity. I get a porn site when I click
on the link and I also get a panel that says the link is no longer
valid. Are others seeing the same thing?
Thanks, Steve Hammond
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
To leave this list email PSN-L-REQUEST@.............. with
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.
Subject: Has http://quake.wr.usgs.gov/ been=20
hacked?
I think this link has been hacked. http://quake.wr.usgs.gov/ It =
should be=20
the local California seismic activity. I get a porn site when I =
click on=20
the link and I also get a panel that says the link is no =
longer valid. Are=20
others seeing the same thing? Thanks, Steve=20
=
Hammond
To leave this list email =
PSN-L-REQUEST@...............
=20
with the body of the message (first line only): unsubscribe See =
http://www.seismicnet.co=
m/maillist.html=20
for more information.
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
From: Chuck Erickson cee@.............
Date: Mon, 12 Mar 2007 12:25:39 -0700
It works fine for me,
Chuck
At 12:09 PM 3/12/2007 -0700, you wrote:
>I think this link has been hacked. http://quake.wr.usgs.gov/ It should
>be the local California seismic activity. I get a porn site when I click
>on the link and I also get a panel that says the link is no longer
>valid. Are others seeing the same thing?
>Thanks, Steve Hammond
>
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with
>the body of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.
Chuck Erickson mailto:cee@.............
Principal
CECO Associates http://www.cecoassoc.com
PO Box 3703
Saratoga, CA 95070
Ph:+(408) 741-5769 Fax:+(408) 741-5386 Cell:+(408) 314-9090
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
From: "Bob Hammond" propgrinder@.........
Date: Mon, 12 Mar 2007 11:24:46 -0800
It's correct for me, Steve.
Bob Hammond
PSN-Alaska
http://wulik.com
On 3/12/07, Chuck Erickson wrote:
>
> It works fine for me,
>
> Chuck
>
> At 12:09 PM 3/12/2007 -0700, you wrote:
> >I think this link has been hacked. http://quake.wr.usgs.gov/ It should
> >be the local California seismic activity. I get a porn site when I click
> >on the link and I also get a panel that says the link is no longer
> >valid. Are others seeing the same thing?
> >Thanks, Steve Hammond
> >
> >__________________________________________________________
> >
> >Public Seismic Network Mailing List (PSN-L)
> >
> >To leave this list email PSN-L-REQUEST@.............. with
> >the body of the message (first line only): unsubscribe
> >See http://www.seismicnet.com/maillist.html for more information.
>
> Chuck Erickson mailto:cee@.............
> Principal
> CECO Associates http://www.cecoassoc.com
> PO Box 3703
> Saratoga, CA 95070
> Ph:+(408) 741-5769 Fax:+(408) 741-5386 Cell:+(408) 314-9090
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
It's correct for me, Steve.
At 12:09 PM 3/12/2007 -0700, you wrote:
>I think this link has been hacked. http://quake.wr.usgs.gov/ It should >be the local California seismic activity. I get a porn site when I click >on the link and I also get a panel that says the link is no longer
>valid. Are others seeing the same thing? >Thanks, Steve Hammond > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) >
>To leave this list email PSN-L-REQUEST@.............. with >the body of the message (first line only): unsubscribe >See
http://www.seismicnet.com/maillist.html for more information.
Chuck Erickson mailto:cee@............. Principal CECO Associates
http://www.cecoassoc.com PO Box 3703 Saratoga, CA 95070 Ph:+(408) 741-5769 Fax:+(408) 741-5386 Cell:+(408) 314-9090
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
From: ChrisAtUpw@.......
Date: Mon, 12 Mar 2007 15:25:50 EDT
In a message dated 2007/03/12, shammon1@............. writes:
> I think this link has been hacked. http://quake.wr.usgs.gov/ It should
> be the local California seismic activity. I get a porn site when I click
> on the link
Hi Steve,
This link is still USGS as it is supposed to be, from the UK.
Maybe your computer got infected ? Can you check what the link is
actually calling? Or your service provider ?
Regards,
Chris Chapman
In a me=
ssage dated 2007/03/12, shammon1@............. writes:
I think this link has been hack=
ed. http://quake.wr.usgs.gov/ It should
be the local California seismic activity. I get a porn site when I click
on the link
Hi Steve,
This link is still USGS as it is suppos=
ed to be, from the UK.
Maybe your computer got infected ? Can=20=
you check what the link is actually calling? Or your service provider ?
Regards,
Chris Chapman =20
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
From: Bob Fryer bfryer@............
Date: Mon, 12 Mar 2007 12:30:29 -0800
Steve,
It works alright for me.
E-mail program has been acting weird since Saturday night DST change.
Bob
On Mar 12, 2007, at 11:09 AM, Stephen Hammond wrote:
> I think this link has been hacked. http://quake.wr.usgs.gov/ It should
> be the local California seismic activity. I get a porn site when I
> click
> on the link and I also get a panel that says the link is no longer
> valid. Are others seeing the same thing?
> Thanks, Steve Hammond
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
From: Larry Conklin lconklin@............
Date: Mon, 12 Mar 2007 16:46:57 -0400
It sounds to me like some sort of maleware has altered your hosts file.
The hosts file is the first place your browser looks to resolve a
site address into the actual IP address that is used to access the site.
So if the IP address that is associated with http://quake.wr.usgs.gov/
gets changed to a porn site, that's where you wind up. If you do a
Google search on "hosts file" you will find a lot of information that
will help you locate it on your system and clean it up. I'm sure that
there are a lot of tools that you can find that will make the job
easier, and a lot of security tools will prevent maleware from making
alterations to your hosts file.
Stephen Hammond wrote:
> I think this link has been hacked. http://quake.wr.usgs.gov/ It should
> be the local California seismic activity. I get a porn site when I click
> on the link and I also get a panel that says the link is no longer
> valid. Are others seeing the same thing?
> Thanks, Steve Hammond
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Unfortunate Explosion
From: "Randy" rpratt@.............
Date: Mon, 12 Mar 2007 21:30:08 -0600
Hi All,
I returned from a short family vacation to find a house in the =
neighborhood about .5 km from me had exploded and leveled leaving the =
house on either side also destroyed. I have posted my plots at =
http://mit.midco.net/rpratt The explosion was caused by a gas line in =
the street cracking and fortunately nobody was home at the time. The =
velocity plot is a N-S Lehman and the displacement is a 1.35 sec =
vertical with both filtered to 1 sec high pass.
Randy
Hi All,
I returned from a short family vacation =
to find a=20
house in the neighborhood about .5 km from me had exploded and leveled =
leaving=20
the house on either side also destroyed. I have posted my plots at =
http://mit.midco.net/rpratt =
; The=20
explosion was caused by a gas line in the street cracking and =
fortunately nobody=20
was home at the time. The velocity plot is a N-S Lehman and the=20
displacement is a 1.35 sec vertical with both filtered to 1 sec high=20
pass.
Randy
Subject: Daylight savings time?
From: "tchannel" tchannel@..............
Date: Mon, 12 Mar 2007 22:00:16 -0600
I am not thinking very clearly tonight. Here is my question... I am in =
the Mountain time zone, now Mountain Daylight time.
Standard Mountain time is GMT-7 So I guess Mountain Daylight time is =
GMT -6
I change all the clocks and the computer ahead one hour.
I just recorded the 5.5m Gulf of California, but I see the helicorder on =
AmaSeis showing it at 03:59 instead of the correct UTC of 02:59. So my =
AmaSeis clock is off (fast) one hour, but the computer clock is correct, =
for Mountain Daylight Time.
Do I need to reset AmaSeis somehow? Thanks, Ted
I am not thinking very clearly =
tonight. Here=20
is my question... I am in the Mountain time zone, now Mountain Daylight=20
time.
Standard Mountain time is GMT-7 =
So I guess=20
Mountain Daylight time is GMT -6
I change all the clocks and the =
computer ahead one=20
hour.
I just recorded the 5.5m Gulf of =
California, but I=20
see the helicorder on AmaSeis showing it at 03:59 instead of the correct =
UTC of=20
02:59. So my AmaSeis clock is off (fast) one hour, but the =
computer=20
clock is correct, for Mountain Daylight Time.
Do I need to reset AmaSeis =
somehow? =20
Thanks, Ted
Subject: Re: Daylight savings time?
From: Stephen & Kathy skmort@............
Date: Mon, 12 Mar 2007 21:36:14 -0700
Here are two ideas,, patch your operating system,, or go in and tell
AmaSeis that you are at the next time zone back for a couple of weeks
until your system catches up on the first Sunday of April, at which time
you will have to reset both your computer and AmaSeis!! I'm running
windows 98 SE and patched with:
http://www.intelliadmin.com/DaylightSavingNotice.asp?File=DaylightSavingFix98.exe
Stephen
PSN Station #55
tchannel wrote:
> I am not thinking very clearly tonight. Here is my question... I am
> in the Mountain time zone, now Mountain Daylight time.
> Standard Mountain time is GMT-7 So I guess Mountain Daylight time is
> GMT -6
> I change all the clocks and the computer ahead one hour.
> I just recorded the 5.5m Gulf of California, but I see the helicorder
> on AmaSeis showing it at 03:59 instead of the correct UTC of 02:59.
> So my AmaSeis clock is off (fast) one hour, but the computer clock is
> correct, for Mountain Daylight Time.
> Do I need to reset AmaSeis somehow? Thanks, Ted
Here are two ideas,, patch your operating system,, or go in and tell
AmaSeis that you are at the next time zone back for a couple of weeks
until your system catches up on the first Sunday of April, at which
time you will have to reset both your computer and AmaSeis!! I'm
running windows 98 SE and patched with:
I am not thinking very clearly
tonight. Here is my question... I am in the Mountain time zone, now
Mountain Daylight time.
Standard Mountain time is GMT-7 So
I guess Mountain Daylight time is GMT -6
I change all the clocks and the
computer ahead one hour.
I just recorded the 5.5m Gulf of
California, but I see the helicorder on AmaSeis showing it at 03:59
instead of the correct UTC of 02:59. So my AmaSeis clock is off
(fast) one hour, but the computer clock is correct, for Mountain
Daylight Time.
Do I need to reset AmaSeis
somehow? Thanks, Ted
Subject: Re: Daylight savings time?
From: John or Jan Lahr JohnJan@........
Date: Mon, 12 Mar 2007 23:47:44 -0700
AmaSeis figures out GMT from the PC clock, assuming that the Time
Zone of the PC is set correctly.
The date and time properties on my office WinXP PC say GMT-8, the box
is checked for "adjust clock for daylight savings changes," and the
time changed correctly and automatically on March 11.
However, for Win98 and earlier Microsoft does not supply an easy fix
that I know about.
Here are some options:
Set the clock to standard time, do not check the box for "adjust
clock for daylight savings changes," and keep in mind that the PC
will remain in "standard time" all year round.
Just leave the time set to standard time, check the box for "adjust
clock for daylight savings changes," and keep in mind that the PC
will switch to "daylight savings time" according to the old
dates. That's what I'm doing with my AmaSeis Win98 PC.
Try one of the programs given on this page (TZEDIT or Zone Manager):
http://www.mdgx.com/add.htm#TZU
These programs adjust the registry entries that set the start and end
dates of daylight savings.
I checked the educational records located here:
http://jclahr.com/science/psn/as1/heli/allas1.php
and all but one show the Gulf event's surface waves within the 3rd
hour. The exception is Duluth,
http://jclahr.com/science/psn/as1/heli/duluth.html
where the PC clock was probably adjusted "by hand" to the new time
without using TZEDIT.
Since AmaSeis didn't "know" that the clock adjustment was for
daylight savings time, the data are being written to the wrong hours.
Hope this helps!
John
At 09:00 PM 3/12/2007, you wrote:
>I am not thinking very clearly tonight. Here is my question... I am
>in the Mountain time zone, now Mountain Daylight time. Standard
>Mountain time is GMT-7 So I guess Mountain Daylight time is GMT -6
>I change all the clocks and the computer ahead one hour.
>I just recorded the 5.5m Gulf of California, but I see the
>helicorder on AmaSeis showing it at 03:59 instead of the correct UTC
>of 02:59. So my AmaSeis clock is off (fast) one hour, but the
>computer clock is correct, for Mountain Daylight Time.
>Do I need to reset AmaSeis somehow? Thanks, Ted
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: Has http://quake.wr.usgs.gov/ been hacked?
From: "Steve Hammond" shammon1@.............
Date: Tue, 13 Mar 2007 10:41:42 -0700
Thanks for the quick response from everybody. I also received a few
suggestions off-line. I didn't take any action or do anything and the
issue went away just a quickly as it started. John, the link was
http://quake.wr.usgs.gov/recenteqs/latest.html and it failed from the
link on the main page on the PSN San Jose web page housed at Earthlink.
It also crashed when I put the URL in the navigation bar in IE which
promted me to post the question to the list. I do run McaFee and Spybot
on all my systems and I ran a full scan with both products this morning
and other than a bunch of cookies it looks like nothing got hammered. I
also FTP'ed to the PSN SJ website on Earthlink and the page has not been
altered.
No Jan <> I was not out cruzing the porn sites. However I tend to
agree with Larry's analysis about mal-ware. I remember receiving a
warning message from Spybot earlier yesterday after doing a search in
Google for a "granite stone shower soap dish." (I'm getting ready to
tile a bathtub area.) And the message said I was clicking on a link that
was known to plant mal-ware and it (Spybot) was blocking the browser
from going to the URL. Maybe it got me before the browser stopped?
Anyway, now all seems well with the world. However, just to play it safe
after reading Larry's comments, I'm flushing the cache on that system in
the event there are traces still around.
Thanks for all the help.
Steve Hammond PSN
-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@...............
On Behalf Of Larry Conklin
Sent: Monday, March 12, 2007 1:47 PM
To: psn-l@..............
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
It sounds to me like some sort of maleware has altered your hosts file.
The hosts file is the first place your browser looks to resolve a
site address into the actual IP address that is used to access the site.
So if the IP address that is associated with http://quake.wr.usgs.gov/
gets changed to a porn site, that's where you wind up. If you do a
Google search on "hosts file" you will find a lot of information that
will help you locate it on your system and clean it up. I'm sure that
there are a lot of tools that you can find that will make the job
easier, and a lot of security tools will prevent maleware from making
alterations to your hosts file.
Stephen Hammond wrote:
> I think this link has been hacked. http://quake.wr.usgs.gov/ It
> should be the local California seismic activity. I get a porn site
> when I click on the link and I also get a panel that says the link is
> no longer valid. Are others seeing the same thing? Thanks, Steve
> Hammond
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
From: ChrisAtUpw@.......
Date: Tue, 13 Mar 2007 14:42:23 EDT
In a message dated 2007/03/13, shammon1@............. writes:
> I do run McaFee and Spybot on all my systems
Hi Steve,
I suggest that you check that McAfee and Spybot are compatible. I use
a different virus program and after experiencing some problems, I was warned
that Spybot was not compatible with it.
Regards,
Chris Chapman
In a me=
ssage dated 2007/03/13, shammon1@............. writes:
I do run McaFee and Spybot on=20=
all my systems
Hi Steve,
I suggest that you check that McAfee an=
d Spybot are compatible. I use a different virus program and after experienc=
ing some problems, I was warned that Spybot was not compatible with it.
Regards,
Chris Chapman =20
Subject: RE: Has http://quake.wr.usgs.gov/ been hacked?
From: "Stephen Hammond" shammon1@.............
Date: Tue, 13 Mar 2007 11:50:46 -0700
Hi Chris, Oops. I did it again. I purchased Webroot Spy Sweeper and I
keep calling it SpyBot which it replaced. S--
-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@...............
On Behalf Of ChrisAtUpw@.......
Sent: Tuesday, March 13, 2007 11:42 AM
To: psn-l@..............
Subject: Re: Has http://quake.wr.usgs.gov/ been hacked?
In a message dated 2007/03/13, shammon1@............. writes:
I do run McaFee and Spybot on all my systems
Hi Steve,
I suggest that you check that McAfee and Spybot are compatible. I
use a different virus program and after experiencing some problems, I
was warned that Spybot was not compatible with it.
Regards,
Chris Chapman
Hi Chris, =
Oops… I did
it again. I purchased Webroot Spy Sweeper and I keep calling it SpyBot =
which it
replaced. S--