Subject: Re: Digital / Analogue Inverse Filters From: ChrisAtUpw@....... Date: Sat, 31 Dec 2005 21:54:13 EST In a message dated 31/12/2005, Bobhelenmcclure@....... writes: > If you should still want to try to extend the low frequency response of > a 4.5Hz geophone, I have implemented a digital inverse filter which can > operate on PSN Type 4 files. The application is "WQFilter.exe". To download it, > go to > http://www.jclahr.com/science/psn/mcclure/wdq_utilities/index.html > and download the file "seismic_dataq.zip". Extract "WQFilter.exe" and > "WQFilterHlp.txt" from the zip file. > > My personal opinion is that trying to use a 4.5Hz geophone is a pretty > futile exercise for most amateur seismologists, unless you have an interest in > local cultural noise or are sitting on top of an active volcano. I use > moderate period homebuilt sensors for my station. They range in natural period > from ~5 seconds to ~15 seconds, and for them, the use of "WQFilter" yields event > waveforms closely resembling those recorded by professional long period > instruments. I use oversampling and DC amplifiers as well for data acquisition. Hi Bob, Thanks for the comments. The negative side of trying to do x10 digital frequency extension for 4.5 Hz geophones is two fold. The low frequency signals are inherently small and grainy and most 16 bit ADCs have 2 to 3 bits of noise on them. This noise can be averaged out by oversampling, as you mention, but you do need to do it with a processor on the ADC board. You need four times the number of samples for each bit of ADC noise that you want to average out -> 64 samples per reading for 3 bits of noise. Normal communication software does not let you take enough samples quickly enough, using just the main data logging computer. 24 bit ADCs have built in averaging, but you could still see 1/f noise. Roberts' original circuit used a two stage low pass filter. This allowed the very low frequency 1/f circuit noise to be amplified along with the signal. Changes to the circuit design have removed most of the VLF noise sensitivity. The noise on the compensated signal is certainly higher than I would get with a new $1000 1 Hz geophone, but it is still significantly below the ambient + cultural noise that I experience. This analogue technique is viable and it can be made to work reasonably well. I agree with your rather more pessimistic opinion of the digital technique for 4.5 Hz geophones. If you want a period extension of less than x4, the digital method should work OK. I wish everyone a less traumatic year for 2006! Chris Chapman In a message dated 31/12/2005, Bobh= elenmcclure@....... writes:

    If you shoul= d still want to try to extend the low frequency response of a 4.5Hz geophone= , I have implemented a digital inverse filter which can operate on PSN Type=20= 4 files. The application is "WQFilter.exe". To download it, go to
   http://www.jclahr.com/science/psn/mcclure/wdq_utilities/inde= x.html
and download the file "seismic_dataq.zip". Extract "WQFilter.exe" and "WQFil= terHlp.txt" from the zip file.
 
    My personal opinion is that trying to use a 4.5Hz geophon= e is a pretty futile exercise for most amateur seismologists, unless you hav= e an interest in local cultural noise or are sitting on top of an active vol= cano. I use moderate period homebuilt sensors for my station. They range in=20= natural period from ~5 seconds to ~15 seconds, and for them, the use of "WQF= ilter" yields event waveforms closely resembling those recorded by professio= nal long period instruments. I use oversampling and DC amplifiers as well fo= r data acquisition.


Hi Bob,

       Thanks for the comments. The negative s= ide of trying to do x10 digital frequency extension for 4.5 Hz geophones is=20= two fold. The low frequency signals are inherently small and grainy and most= 16 bit ADCs have 2 to 3 bits of noise on them. This noise can be averaged o= ut by oversampling, as you mention, but you do need to do it with a proce= ssor on the ADC board. You need four times the number of samples for eac= h bit of ADC noise that you want to average out -> 64 samples per reading= for 3 bits of noise. Normal communication software does not let you take en= ough samples quickly enough, using just the main data logging computer. 24 b= it ADCs have built in averaging, but you could still see 1/f noise.

       Roberts' original circuit used a two st= age low pass filter. This allowed the very low frequency 1/f circuit noise t= o be amplified along with the signal. Changes to the circuit design have rem= oved most of the VLF noise sensitivity. The noise on the compensated signal=20= is certainly higher than I would get with a new $1000 1 Hz geophone, but it=20= is still significantly below the ambient + cultural noise that I expe= rience. This analogue technique is viable and it can be made to work reasona= bly well.

       I agree with your rather more pessimist= ic opinion of the digital technique for 4.5 Hz geophones. If you want a peri= od extension of less than x4, the digital method should work OK.

       I wish everyone a less traumatic year f= or 2006!

       Chris Chapman Subject: from Angel with soem traces. From: Angel sismos@.............. Date: Mon, 2 Jan 2006 23:28:00 +0000 Happy New year to all! Quite a bit of shaking in the last few days and I have some jpg's I would like share and get comment on. Both the traces are from the experimenta FMES (Dave Nelson) seismographs. My basic setup is This instrument has a long period cutoff of 275 seconds. The response is velocity with the integration below 25 seconds from the hydraulic damping and from 25 seconds to 275 seconds from electronic integration One is from the Sandwich Island quake and the other is from the one just of the coast of Panama a few days ago. http://volcanbaru.com/nelson/sandwich.jpg http://volcanbaru.com/nelson/61panama.jpg In the 6.1 from Panama the inset if has a low pass of 0.3 and I think that the big dip is real. The middle of the sandwich trace the period is about 60 seconds. Each line is 120 minutes. Larry is there any way to post any ole GIF to the recent event on the PSN list?? regards to all. Angel __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: from Angel with soem traces. From: Mike Speed mike8s2@......... Date: Mon, 2 Jan 2006 18:50:32 -0800 (PST) http://volcanbaru.com/nelson/sandwich.jpg http://volcanbaru.com/nelson/61panama.jpg ------------------ Hi Angel, Would you please tell me what software these traces were produced on? Thanks, Greg --------------------------------- Yahoo! Shopping Find Great Deals on Holiday Gifts at Yahoo! Shopping
http://volcanbaru.com/nelson/sandwich.jpg
http://volcanbaru.com/nelson/61panama.jpg


------------------

Hi Angel,

Would you please tell me what software these traces were produced on?

Thanks,

Greg

Yahoo! Shopping
Find Great Deals on Holiday Gifts at Yahoo! Shopping Subject: Re: from Angel with soem traces. From: Larry Cochrane lcochrane@.............. Date: Mon, 02 Jan 2006 23:34:32 -0800 Happy New Years Everyone, Angel Wrote: > Larry is there any way to post any ole GIF to the recent event on the > PSN list?? No, sorry all attachments are blocked by my mail server. You will need to place them on a web server and send out the URL. Regards, Larry Cochrane Redwood City, PSN __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re[2]: from Angel with some traces. From: Angel sismos@.............. Date: Tue, 3 Jan 2006 09:36:52 +0000 Hello Larry, What meant to say was "is there any way to post any ole GIF to the recent event list on the PSN page? I understand the list does not accept attachments? Angel Tuesday, January 3, 2006, 7:34:32 AM, you wrote: >> Larry is there any way to post any ole GIF to the recent event on the >> PSN list?? > No, sorry all attachments are blocked by my mail server. You will need to place them > on a web server and send out the URL. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Swarm software From: Angel sismos@.............. Date: Tue, 3 Jan 2006 09:47:07 +0000 Hello Greg, These traces were produced on Swarm a program written by Dan Cervalli and used USGS Volcano Observatories. The software is freely available and reads data from Earthworm waveservers or from SEED files. It gets its data over TCP/IP. So Dave in LA can see in real time the traces from my seismograph here in Panama. Larry's WinSDR boards now communicate with Earthworm so in theory a person could run WinSDR and turn the data sever, I could capture here and see it with a small delay and display it in Swarm. Angel Tuesday, January 3, 2006, 2:50:32 AM, you wrote: > http://volcanbaru.com/nelson/sandwich.jpg > http://volcanbaru.com/nelson/61panama.jpg > ------------------ > Hi Angel, > Would you please tell me what software these traces were produced on? > Thanks, > Greg __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: from Angel with some traces. From: Larry Cochrane lcochrane@.............. Date: Tue, 03 Jan 2006 19:36:47 -0800 Hi Angel, To archive event files on my system you need to send the file in PSN format to the following email address event@............... GIF files will not be excepted since the event file must be in the PSN binary format. Regards, Larry Cochrane Redwood City, PSN Angel wrote: > Hello Larry, > > What meant to say was "is there any way to post any ole GIF to the recent > event list on the PSN page? > > I understand the list does not accept attachments? > > Angel > > > Tuesday, January 3, 2006, 7:34:32 AM, you wrote: > >>> Larry is there any way to post any ole GIF to the recent event on the >>> PSN list?? > >> No, sorry all attachments are blocked by my mail server. You will need to place them >> on a web server and send out the URL. > > > __________________________________________________________ > > 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: Swarm software From: Larry Cochrane lcochrane@.............. Date: Tue, 03 Jan 2006 23:26:14 -0800 Hi Everyone, Angel wrote: > Larry's WinSDR boards now communicate with Earthworm so in theory a > person could run WinSDR and turn the data sever, I could capture here > and see it with a small delay and display it in Swarm. More information on my Earthworm modules can be found here http://www.seismicnet.com/software.html#Earthworm. Regards, Larry Cochrane Redwood City, PSN __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Gulf Of California on a seismic Detector From: "Geoff" gmvoeth@........... Date: Wed, 4 Jan 2006 02:30:43 -0700 Hello Folks; http://users.isp.com/gmvoethb293690/B.MOV This is a MOV file about 3.11MB 15 seconds of video showing my seismic detector in action during the recent quake in the Gulf of California. http://earthquake.usgs.gov/recenteqsww/Quakes/ushmal.htm I do not know if you will be able to download directly from my website but I encourage you to try and tell me if you were successful or not. If you can not download I will seek another site that allows such things. I am not selling anything here just want to share what it looks like. The buzzer is about 4000Hz but no audio in this MOV file. Comments are welcome. Sincerely; Geoff __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Gulf Of California on a seismic Detector From: Angel sismos@.............. Date: Wed, 4 Jan 2006 10:00:51 +0000 Hello Geoff, What a great seismoscope. My very first seismic detector was a modified car alarm with a weight on string and all it did was make a noise when someting happened. Nice movie, I saw it with Quicktime. When I clicked on the link I assumed I was going to see a Lehman jumping around or falling over. Here is how it us showing up on my FMES, the event is still going. The traces are one hour long. http://volcanbaru.com/nelson/mexico_1_4.jpg Angel Wednesday, January 4, 2006, 9:30:43 AM, you wrote: > Hello Folks; > http://users.isp.com/gmvoethb293690/B.MOV > This is a MOV file about 3.11MB 15 seconds > of video showing my seismic detector in action > during the recent quake in the Gulf of California. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Gulf Of California on a seismic Detector From: Kevin McCue asc@............... Date: Wed, 4 Jan 2006 21:08:03 +1100 Geoff The movie worked for me. My a2d had trouble with the format but the flickering red neon was a nice extra touch (bit like my sleeping Mac). Good to see you guys get excited about regional earthquakes instead of teles. I run an accelerograph network in and around Canberra, Australia just for the local and regional earthquakes tho it occasionally picks up large deep Fiji events which are good to check the station polarity. Thanks for the movie Cheers Kevin On 04/01/2006, at 8:30 PM, Geoff wrote: > > I do not know if you will be able to download > directly from my website but I encourage you > to try and tell me if you were successful or not. Kevin McCue Director Australian Seismological Centre PO Box 324 Jamison Centre ACT 2614 Australia ph: 61 (0)2 6251 1291 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Gulf Of California on a seismic Detector From: ian ian@........... Date: Wed, 04 Jan 2006 10:19:34 +0000 I saw the mov okay with quicktime. Food for thought, installing a camera. Unfortunately I've just realised that my Lehman oscillates when it is cold. The temperature here declined yesterday afternoon and the thing started oscillating. It's -1C at the moment and the graph looks like I spilled red ink all over it ( http://www.iasmith.com/realtime.htm ) . You can, though, see the California quake sticking out above it all, like the Golden Gate bridge above the fog. When the quake stops I'll turn it into a psn file, which should clean the red ink off of it. I don't rate my chances very highly of finding out what is causing it to oscillate... Ian Smith Kevin McCue wrote: > Geoff > The movie worked for me. My a2d had trouble with the format but the > flickering red neon was a nice extra touch (bit like my sleeping Mac). > Good to see you guys get excited about regional earthquakes instead of > teles. I run an accelerograph network in and around Canberra, > Australia just for the local and regional earthquakes tho it > occasionally picks up large deep Fiji events which are good to check > the station polarity. > Thanks for the movie > Cheers > Kevin > > > On 04/01/2006, at 8:30 PM, Geoff wrote: > >> >> I do not know if you will be able to download >> directly from my website but I encourage you >> to try and tell me if you were successful or not. > > > Kevin McCue > Director > Australian Seismological Centre > PO Box 324 Jamison Centre > ACT 2614 > Australia > ph: 61 (0)2 6251 1291 > > __________________________________________________________ > > 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: Gulf Of California on a seismic Detector From: ChrisAtUpw@....... Date: Wed, 4 Jan 2006 08:59:08 EST In a message dated 04/01/2006, ian@........... writes: Unfortunately I've just realised that my Lehman oscillates when it is cold. The temperature here declined yesterday afternoon and the thing started oscillating. It's -1C at the moment and the graph looks like I spilled red ink all over it ( http://www.iasmith.com/realtime.htm ) . I don't rate my chances very highly of finding out what is causing it to oscillate. Ian Smith Hi Ian, The energy has to be coming from somewhere! If you only see oscillations when the outside air is cold, this is likely to be the driving source. Do you have any photos of the Lehman? Is it housed in it's own sealed box? Does the box have an internal top heater? What suspension system are you using? What damping system do you use? One of the ways you can get 'oscillations' from a Lehman, is if the box and internal instrument is warmer than the outside air, but there is no top heater inside the box to maintain a stable vertical temperature gradient. Rolls of cooler air break off the inside top / sides of the box when the thermal gradient gets big enough and then interact with the boom. You only need a few watts of power into Al housed power resistors bolted to a 1/16" Al top plate inside the top of case. Is the top of the box completely sealed? How is it 'sealed' to the floor? Can drafts / air currents get in? One way to 'semi seal' the housing is to surround the box with a 2" high wood rectangle on the floor and fill the gap with dry sand. Worth trying? Regards, Chris Chapman
In a message dated 04/01/2006, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Unfortunately I've just realised that my Lehman oscillates when i= t is=20
cold. The temperature here declined yesterday afternoon and the t= hing=20
started oscillating. It's -1C=20 at the moment and the graph looks like I
spilled red ink all over it (= =20 http://www.iasmith.com/realtime.htm ) . 

I don't rate my chan= ces=20 very highly of finding out what is causing it to
oscillate.

Ian= =20 Smith
Hi Ian,
 
    The energy has to be coming from somewhere! If=20= you=20 only see oscillations when the outside air is cold, this is likely to be the= =20 driving source.
 
    Do you have any photos of the Lehman? Is it hou= sed=20 in it's own sealed box? Does the box have an internal top heater? What=20 suspension system are you using? What damping system do you use?
 
    One of the ways you can get 'oscillations' from= a=20 Lehman, is if the box and internal instrument is warmer than the=20 outside air, but there is no top heater inside the box to maintain a stable=20 vertical temperature gradient. Rolls of cooler air break off the inside= top=20 / sides of the box when the thermal gradient gets big enough and then intera= ct=20 with the boom. 
 
    You only need a few watts of power into Al hous= ed=20 power resistors bolted to a 1/16" Al top plate inside the top of case.
 
    Is the top of the box completely sealed? How is= it=20 'sealed' to the floor? Can drafts / air currents get in? One way to 'semi se= al'=20 the housing is to surround the box with a 2" high wood rectangle on the= =20 floor and fill the gap with dry sand.
 
    Worth trying?
 
    Regards,
 
    Chris Chapman
Subject: ebay auction From: Bob Barns royb1@........... Date: Wed, 04 Jan 2006 09:38:02 -0500 seismometer, short-period AKA shot-pot for oil survey Item number: 7578330430 ends Jan 10 Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Gulf Of California on a seismic Detector From: ian ian@........... Date: Wed, 04 Jan 2006 14:53:43 +0000 Hi, thanks for the reply, I'm still working through it! In the meantime, I don't have any good pictures but here is a drawing of the housing that I just quickly sketched: http://www.iasmith.com/housing.jpg . Let me know if the link doesn't work. I have no heater. I had hoped to avoid one but sounds like I need to consider it. It's just the usual wire diagonal from the top of the boom. The pivot consists of 2 ball bearings. The boom has a flat metal plate on the end which pivots on them. I have magnetic damping but it is not properly set up at present. The system is currently under damped. The weight on the end of the boom is copper and this doubles as the magnetic damping. The internal may well be warmer than the outside (a thermometer would be nice addition too!). In theory the box is sealed but nothing is perfect... Perhaps a car battery to power the resistors would solve it. I'll need to wait till I go back to work next week to get some of those heatsunk resistors. Thanks Ian ChrisAtUpw@....... wrote: > In a message dated 04/01/2006, ian@........... writes: > > Unfortunately I've just realised that my Lehman oscillates when it is > cold. The temperature here declined yesterday afternoon and the thing > started oscillating. It's -1C at the moment and the graph looks > like I > spilled red ink all over it ( http://www.iasmith.com/realtime.htm > ) . > > I don't rate my chances very highly of finding out what is causing > it to > oscillate. > > Ian Smith > > Hi Ian, > > The energy has to be coming from somewhere! If you only see > oscillations when the outside air is cold, this is likely to be the > driving source. > > Do you have any photos of the Lehman? Is it housed in it's own > sealed box? Does the box have an internal top heater? What suspension > system are you using? What damping system do you use? > > One of the ways you can get 'oscillations' from a Lehman, is if > the box and internal instrument is warmer than the outside air, but > there is no top heater inside the box to maintain a stable vertical > temperature gradient. Rolls of cooler air break off the inside top / > sides of the box when the thermal gradient gets big enough and then > interact with the boom. > > You only need a few watts of power into Al housed power resistors > bolted to a 1/16" Al top plate inside the top of case. > > Is the top of the box completely sealed? How is it 'sealed' to the > floor? Can drafts / air currents get in? One way to 'semi seal' the > housing is to surround the box with a 2" high wood rectangle on the > floor and fill the gap with dry sand. > > Worth trying? > > Regards, > > Chris Chapman Hi,

thanks for the reply, I'm still working through it!  In the meantime, I don't have any good pictures but here is a drawing of the housing that I just quickly sketched: http://www.iasmith.com/housing.jpg .  Let me know if the link doesn't work.

I have no heater.  I had hoped to avoid one but sounds like I need to consider it.

It's just the usual wire diagonal from the top of the boom.  The pivot consists of 2 ball bearings.  The boom has a flat metal plate on the end which pivots on them.  I have magnetic damping but it is not properly set up at present.  The system is currently under damped.  The weight on the end of the boom is copper and this doubles as the magnetic damping.

The internal may well be warmer than the outside (a thermometer would be nice addition too!).  In theory the box is sealed but nothing is perfect...

Perhaps a car battery to power the resistors would solve it.  I'll need to wait till I go back to work next week to get some of those heatsunk resistors.

Thanks

Ian

ChrisAtUpw@....... wrote:
In a message dated 04/01/2006, ian@........... writes:
Unfortunately I've just realised that my Lehman oscillates when it is
cold. The temperature here declined yesterday afternoon and the thing
started oscillating. It's -1C at the moment and the graph looks like I
spilled red ink all over it ( http://www.iasmith.com/realtime.htm ) . 

I don't rate my chances very highly of finding out what is causing it to
oscillate.

Ian Smith
Hi Ian,
 
    The energy has to be coming from somewhere! If you only see oscillations when the outside air is cold, this is likely to be the driving source.
 
    Do you have any photos of the Lehman? Is it housed in it's own sealed box? Does the box have an internal top heater? What suspension system are you using? What damping system do you use?
 
    One of the ways you can get 'oscillations' from a Lehman, is if the box and internal instrument is warmer than the outside air, but there is no top heater inside the box to maintain a stable vertical temperature gradient. Rolls of cooler air break off the inside top / sides of the box when the thermal gradient gets big enough and then interact with the boom. 
 
    You only need a few watts of power into Al housed power resistors bolted to a 1/16" Al top plate inside the top of case.
 
    Is the top of the box completely sealed? How is it 'sealed' to the floor? Can drafts / air currents get in? One way to 'semi seal' the housing is to surround the box with a 2" high wood rectangle on the floor and fill the gap with dry sand.
 
    Worth trying?
 
    Regards,
 
    Chris Chapman
Subject: Re: Gulf Of California on a seismic Detector From: ian ian@........... Date: Wed, 04 Jan 2006 15:47:42 +0000 I've just introduced an angle-pois light with an energy saving 11 Watt bulb into the box as an experiment and temporary measure. It may take an hour or two to have an effect... Ian Smith ChrisAtUpw@....... wrote: > In a message dated 04/01/2006, ian@........... writes: > > Unfortunately I've just realised that my Lehman oscillates when it is > cold. The temperature here declined yesterday afternoon and the thing > started oscillating. It's -1C at the moment and the graph looks > like I > spilled red ink all over it ( http://www.iasmith.com/realtime.htm > ) . > > I don't rate my chances very highly of finding out what is causing > it to > oscillate. > > Ian Smith > > Hi Ian, > > The energy has to be coming from somewhere! If you only see > oscillations when the outside air is cold, this is likely to be the > driving source. > > Do you have any photos of the Lehman? Is it housed in it's own > sealed box? Does the box have an internal top heater? What suspension > system are you using? What damping system do you use? > > One of the ways you can get 'oscillations' from a Lehman, is if > the box and internal instrument is warmer than the outside air, but > there is no top heater inside the box to maintain a stable vertical > temperature gradient. Rolls of cooler air break off the inside top / > sides of the box when the thermal gradient gets big enough and then > interact with the boom. > > You only need a few watts of power into Al housed power resistors > bolted to a 1/16" Al top plate inside the top of case. > > Is the top of the box completely sealed? How is it 'sealed' to the > floor? Can drafts / air currents get in? One way to 'semi seal' the > housing is to surround the box with a 2" high wood rectangle on the > floor and fill the gap with dry sand. > > Worth trying? > > Regards, > > Chris Chapman I've just introduced an angle-pois light with an energy saving 11 Watt bulb into the box as an experiment and temporary measure.  It may take an hour or two to have an effect...

Ian Smith

ChrisAtUpw@....... wrote:
In a message dated 04/01/2006, ian@........... writes:
Unfortunately I've just realised that my Lehman oscillates when it is
cold. The temperature here declined yesterday afternoon and the thing
started oscillating. It's -1C at the moment and the graph looks like I
spilled red ink all over it ( http://www.iasmith.com/realtime.htm ) . 

I don't rate my chances very highly of finding out what is causing it to
oscillate.

Ian Smith
Hi Ian,
 
    The energy has to be coming from somewhere! If you only see oscillations when the outside air is cold, this is likely to be the driving source.
 
    Do you have any photos of the Lehman? Is it housed in it's own sealed box? Does the box have an internal top heater? What suspension system are you using? What damping system do you use?
 
    One of the ways you can get 'oscillations' from a Lehman, is if the box and internal instrument is warmer than the outside air, but there is no top heater inside the box to maintain a stable vertical temperature gradient. Rolls of cooler air break off the inside top / sides of the box when the thermal gradient gets big enough and then interact with the boom. 
 
    You only need a few watts of power into Al housed power resistors bolted to a 1/16" Al top plate inside the top of case.
 
    Is the top of the box completely sealed? How is it 'sealed' to the floor? Can drafts / air currents get in? One way to 'semi seal' the housing is to surround the box with a 2" high wood rectangle on the floor and fill the gap with dry sand.
 
    Worth trying?
 
    Regards,
 
    Chris Chapman
Subject: Re: Gulf Of California on a seismic Detector From: ChrisAtUpw@....... Date: Wed, 4 Jan 2006 11:25:14 EST In a message dated 04/01/2006, ian@........... writes: Hi, thanks for the reply, I'm still working through it! In the meantime, I don't have any good pictures but here is a drawing of the housing that I just quickly sketched: _http://www.iasmith.com/housing.jpg_ (http://www.iasmith.com/housing.jpg) . I have no heater. I had hoped to avoid one but sounds like I need to consider it. Hi Ian, It is not very easy to seal the open top of a box like this. You might be able to do it with foam strip around the edge or the bottom of the thermawall cavity board plug. I would be inclined to get a big sheet of polythene (~9ft square damp proof membrane?) from a builder's merchant, drape it over the top and to the ground all around the box, fold in the corners and secure them with tape or string. This is in place of the multi layer paper sheet. Alternatively, you could use gaffer tape either to seal the paper to the sides of the box, or tape the existing top sheet to a surrounding paper wrap. Then put the sarking board lid on the box. I suspect that you will need some form of heating inside the case. You will probably need at least 10 watts. Power resistors are preferable to filament bulbs, which tend to attract insects. Can you 'acquire' a large cardboard box to put over the top of the existing case? Regards, Chris Chapman
In a message dated 04/01/2006, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Hi,
thanks for the reply, I'm still working through it! =20= In the=20 meantime, I don't have any good pictures but here is a drawing of the hous= ing=20 that I just quickly sketched: http://www.iasmith.com/housing= ..jpg=20 . 

I have no heater.  I had hoped to avoid one but sounds= =20 like I need to consider it.
Hi Ian,
 
    It is not very easy to seal the open top of a b= ox=20 like this. You might be able to do it with foam strip around the edge or the= =20 bottom of the thermawall cavity board plug.
 
    I would be inclined to get a big sheet of polyt= hene=20 (~9ft square damp proof membrane?) from a builder's merchant, drape it over=20= the=20 top and to the ground all around the box, fold in the corners and secure the= m=20 with tape or string. This is in place of the multi layer paper sheet.=20 Alternatively, you could use gaffer tape either to seal the paper to th= e=20 sides of the box, or tape the existing top sheet to a surrounding paper wrap= ..=20 Then put the sarking board lid on the box.
 
    I suspect that you will need some form of heati= ng=20 inside the case. You will probably need at least 10 watts. Power resistors a= re=20 preferable to filament bulbs, which tend to attract insects. Can you 'acquir= e' a=20 large cardboard box to put over the top of the existing case?
 
    Regards,
 
    Chris Chapman
Subject: Re: Gulf Of California on a seismic Detector From: ian ian@........... Date: Wed, 04 Jan 2006 16:51:01 +0000 Hi, thanks for the suggestions. I won't be able to get to the shops until next week. I do have an old car lying around the back and I could take out some of the bulb fittings from that and run 12 volts to the box. I think the box is light tight (I'll check tonight) so probably okay for insects. The temperature is about to drop in the next hour or two so I'll see how effective a heat source is from the temporary light I put in. I still access the box every few days as I try to find the optimum settings and I've still to tackle the damping issue, so it has to be reasonably easy to get in and out of. So the plastic sheet sounds like the best solution. The good news is that this morning's Calafornia 6.7 quake saturated my A/D. Good as in a quake 5000 miles away did that. If I can get the oscillations down then I should be able to resolve 4.x teleseismic quakes. One can dream! Thanks again Ian ChrisAtUpw@....... wrote: > In a message dated 04/01/2006, ian@........... writes: > > Hi, > thanks for the reply, I'm still working through it! In the > meantime, I don't have any good pictures but here is a drawing of > the housing that I just quickly sketched: > http://www.iasmith.com/housing.jpg . > > I have no heater. I had hoped to avoid one but sounds like I need > to consider it. > > Hi Ian, > > It is not very easy to seal the open top of a box like this. You > might be able to do it with foam strip around the edge or the bottom > of the thermawall cavity board plug. > > I would be inclined to get a big sheet of polythene (~9ft square > damp proof membrane?) from a builder's merchant, drape it over the top > and to the ground all around the box, fold in the corners and secure > them with tape or string. This is in place of the multi layer paper > sheet. Alternatively, you could use gaffer tape either to seal the > paper to the sides of the box, or tape the existing top sheet to a > surrounding paper wrap. Then put the sarking board lid on the box. > > I suspect that you will need some form of heating inside the case. > You will probably need at least 10 watts. Power resistors are > preferable to filament bulbs, which tend to attract insects. Can you > 'acquire' a large cardboard box to put over the top of the existing case? > > Regards, > > Chris Chapman Hi,

thanks for the suggestions.  I won't be able to get to the shops until next week. I do have an old car lying around the back and I could take out some of the bulb fittings from that and run 12 volts to the box.  I think the box is light tight (I'll check tonight) so probably okay for insects. 

The temperature is about to drop in the next hour or two so I'll see how effective a heat source is from the temporary light I put in.

I still access the box every few days as I try to find the optimum settings and I've still to tackle the damping issue, so it has to be reasonably easy to get in and out of.  So the plastic sheet sounds like the best solution.

The good news is that this morning's Calafornia 6.7 quake saturated my A/D.  Good as in a quake 5000 miles away did that.  If I can get the oscillations down then I should be able to resolve 4.x teleseismic quakes.  One can dream!

Thanks again

Ian

ChrisAtUpw@....... wrote:
In a message dated 04/01/2006, ian@........... writes:
Hi,
thanks for the reply, I'm still working through it!  In the meantime, I don't have any good pictures but here is a drawing of the housing that I just quickly sketched: http://www.iasmith.com/housing.jpg .. 

I have no heater.  I had hoped to avoid one but sounds like I need to consider it.
Hi Ian,
 
    It is not very easy to seal the open top of a box like this. You might be able to do it with foam strip around the edge or the bottom of the thermawall cavity board plug.
 
    I would be inclined to get a big sheet of polythene (~9ft square damp proof membrane?) from a builder's merchant, drape it over the top and to the ground all around the box, fold in the corners and secure them with tape or string. This is in place of the multi layer paper sheet. Alternatively, you could use gaffer tape either to seal the paper to the sides of the box, or tape the existing top sheet to a surrounding paper wrap. Then put the sarking board lid on the box.
 
    I suspect that you will need some form of heating inside the case. You will probably need at least 10 watts. Power resistors are preferable to filament bulbs, which tend to attract insects. Can you 'acquire' a large cardboard box to put over the top of the existing case?
 
    Regards,
 
    Chris Chapman
Subject: Re: Gulf Of California on a seismic Detector From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Wed, 04 Jan 2006 17:07:50 +0000 Hi Geoff and others on Psn postlist. Thanks for the mov file. I will check it out soon. According to emsc-csem the earthquake in gulf of Mexico was 6,8Ms in size. For those who don't know what emsc-csem is, you can check there page here http://www.emsc-csem.org/ I have been looking for news about this earthquake, but i haven't found anything at the moment. But i excpect that aftershocks have been detected yet, at least one that is 4,7 M, but there are problay alot more happening then i see on the emsc-csem page. The pre-quakes prior to the 6,8Ms one was a earthquake that was 4,9mb and a earthquake that was 4,6 M, there is also a time gap of few hours from the first earthquake happens until the big one hits. I assume that there is going to be more earthquakes in that area for next few days or weeks. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Gulf Of California on a seismic Detector From: John or Jan Lahr JohnJan@........ Date: Wed, 04 Jan 2006 09:14:12 -0800 Hi All, Quite a few of the educational seismic stations provided by IRIS recorded the Gulf event. Take a look here during then next 16 hours or so while the Gulf trace is still visible: http://jclahr.com/science/psn/as1/heli/allas1.php The AS1 instruments are simple, not too expensive ($550), and good for education because they look like a diagram of a seismic system. For more details see: http://jclahr.com/science/psn/as1/ The IRIS Seismographs In Schools Program is described here: http://www.iris.washington.edu/edu/AS1.htm If anyone lives near one of the schools with a system, I'm sure the teachers involved would love to talk to you about seismic recording, and it's possible that you could give them a hand with any recording problems. There is a listing of these and other educational stations here: http://www.scieds.com/spinet/spinet_stations.php Cheers, John ##################################/ John C. Lahr #################################/ Emeritus Seismologist ################################/ U.S. Geological Survey ===========================/ Geologic Hazards Team ##############################/ Golden, Colorado #############################//############################## ############################//############################### PO Box 548 /################################ Corvallis, Oregon 97339 /################################## Phone: (541) 758-2699 /============================= Cell: (541) 740-4844 /################################### Fax: (928) 569-0113 /################################## jjpub@........ /#################################### http://jclahr.com/science/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: GULF OF CALIFORNIA INFRASOUND DETECTION From: AHrubetz@....... Date: Wed, 4 Jan 2006 12:27:55 EST Hello All, I have been recording with an infrasound detector on loan from the Geophysical Dept. of Southern Methodist University for several months now. The 6.7 Gulf of California quake is the first event I've been able to correlate with a quake. (see my PSN postings). The local infrasound signal recorded here in Dallas was not caused by a teleatmospheric pressure wave from the quake, but was generated by the seismic surface wave coupling to the atmosphere at my location, causing corresponding vertical movements of the infrasound detector diaphram which in turn disturbed the local atmosphere. The infrasound disturbance was initiated at the same time as the surface waves arrived, and lasted about 15 minutes, the same duration as the surface waves. There was no indication of a teleatmospheric acoustical pressure wave, which would have arrived at my station about 1.3 hours after initiation of the quake. I found this event very interesing and am passing the info along for your possible interest. Regards, Al Hrubetz Dallas, Texas
Hello All,
    I have been recording with an infrasound det= ector on loan from the Geophysical Dept. of Southern Methodist University fo= r several months now.  The 6.7 Gulf of California quake is the first ev= ent I've been able to correlate with a quake.  (see my PSN postings).
    The local infrasound signal recorded here in= Dallas was not caused by a teleatmospheric pressure wave from the quake, bu= t was generated by the seismic surface wave coupling to the atmosphere at my= location, causing corresponding vertical movements of the infrasound detect= or diaphram which in turn disturbed the local atmosphere.  The inf= rasound disturbance was initiated at the same time as the surface waves arri= ved, and lasted about 15 minutes, the same duration as the surface waves.&nb= sp; There was no indication of a teleatmospheric acoustical pressure wave, w= hich would have arrived at my station about 1.3 hours after initiation of th= e quake.
    I found this event very interesing and am pa= ssing the info along for your possible interest.
    Regards,
    Al Hrubetz
    Dallas, Texas
Subject: Re: GULF OF CALIFORNIA INFRASOUND DETECTION From: ChrisAtUpw@....... Date: Wed, 4 Jan 2006 12:50:55 EST In a message dated 04/01/2006, AHrubetz@....... writes: Hello All, I have been recording with an infrasound detector on loan from the Geophysical Dept. of Southern Methodist University for several months now. The 6.7 Gulf of California quake is the first event I've been able to correlate with a quake. (see my PSN postings). The local infrasound signal recorded here in Dallas was not caused by a teleatmospheric pressure wave from the quake, but was generated by the seismic surface wave coupling to the atmosphere at my location Hi Al, Do you have any specification / characteristics for your Infrasound detector setup, please? What sort of array do you use to connect to the atmosphere, please? Regards, Chris Chapman
In a message dated 04/01/2006, AHrubetz@....... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D3>
Hello All,
    I have been recording with an infra= sound=20 detector on loan from the Geophysical Dept. of Southern Methodist Universi= ty=20 for several months now.  The 6.7 Gulf of California quake is the firs= t=20 event I've been able to correlate with a quake.  (see my PSN=20 postings).
    The local infrasound signal recorde= d here=20 in Dallas was not caused by a teleatmospheric pressure wave from the quake= ,=20 but was generated by the seismic surface wave coupling to the atmosphere a= t my=20 location
Hi Al,
 
    Do you have any specification / characteristics= for=20 your Infrasound detector setup, please? What sort of array do you use t= o=20 connect to the atmosphere, please?
 
    Regards,
 
    Chris Chapman
Subject: [Fwd: Your New PSN Event File] From: ian ian@........... Date: Wed, 04 Jan 2006 20:16:39 +0000 I posted my event file for the California quake earlier today. Does the acknowledgment email mean that it has been filed 64 years in the future? If so, what went wrong? Thanks Ian Smith -------- Original Message -------- Subject: Your New PSN Event File Date: Wed, 04 Jan 06 09:47:51 -0800 From: event_processor@.............. To: ian Your event file has been processed. Event File Upload Status: Input Name Archive Path & Name Status 060104.082516.hd0 \quakes\7001\700101.001537.hd0.psn Upload OK Thanks for the upload! I posted my event file for the California quake earlier today.  Does the acknowledgment email mean that it has been filed 64 years in the future?  If so, what went wrong?

Thanks

Ian Smith

-------- Original Message --------
Subject: Your New PSN Event File
Date: Wed, 04 Jan 06 09:47:51 -0800
From: event_processor@..............
To: ian <ian@...........> 


Your event file has been processed.

Event File Upload Status:

Input Name         Archive Path & Name         Status

060104.082516.hd0  \quakes\7001\700101.001537.hd0.psn   Upload OK


Thanks for the upload!
Subject: Re: GULF OF CALIFORNIA INFRASOUND DETECTION From: AHrubetz@....... Date: Wed, 4 Jan 2006 19:39:36 EST Hi Chris, The detector is a Validyne pressure transducer modified by Dr. Chris Haywood at SMU. I don't know what modifications were made, and have borrowed the detector to see if I could record anything of interest with it. There are 8 inlets into a small volume inlet box. A metal diaphram measures pressure variations differentially with respect to a reference pressure in a larger volume. The bridge circuit electronics is contained within the detector and is powered by 12 volts furnished by an external power supply located about 50' from the detector. It has an internal 1 Hz low gain cutoff. I have no specs on the unit. I am only using two of the inlets, connected to two 50' porous hoses extended inline from opposite sides of the detector. Because of space restrictions, the hoses are doubled back on each other at a length of 25'. What type instrument are you using, and have you recorded any quake-related events? Best regards, Al
Hi Chris,
    The detector is a Validyne pressure transduc= er modified by Dr. Chris Haywood at SMU.   I don't know what modif= ications were made, and have borrowed the detector to see if I could record=20= anything of interest with it.   There are 8 inlets into a sma= ll volume inlet box.  A metal diaphram measures pressure variation= s differentially with respect to a reference pressure in a larger volume.&nb= sp; The bridge circuit  electronics is contained within the detect= or and is powered by 12 volts furnished by an external power supply located=20= about 50' from the detector.  It has an internal 1 Hz low gain cutoff.&= nbsp; I have no specs on the unit.  I am only using two of the inl= ets, connected to two 50' porous hoses extended  inline from oppos= ite sides of the detector.  Because of space restrictions, the hoses ar= e doubled back on each other at a length of 25'. 
    What type instrument are you using, and have= you recorded any quake-related events?
    Best regards,
    Al
Subject: Re: GULF OF CALIFORNIA INFRASOUND DETECTION From: ChrisAtUpw@....... Date: Wed, 4 Jan 2006 22:10:18 EST In a message dated 05/01/2006 00:40:06 GMT Standard Time, AHrubetz@....... writes: Hi Chris, The detector is a Validyne pressure transducer modified by Dr. Chris Haywood at SMU. I don't know what modifications were made, and have borrowed the detector to see if I could record anything of interest with it. There are 8 inlets into a small volume inlet box. A metal diaphram measures pressure variations differentially with respect to a reference pressure in a larger volume. The bridge circuit electronics is contained within the detector and is powered by 12 volts furnished by an external power supply located about 50' from the detector. It has an internal 1 Hz low gain cutoff. I have no specs on the unit. I am only using two of the inlets, connected to two 50' porous hoses extended inline from opposite sides of the detector. Because of space restrictions, the hoses are doubled back on each other at a length of 25'. What type instrument are you using, and have you recorded any quake-related events? Hi Al, Lately, I have been mostly occupied with a seismometers for schools project. One of the sensor types that I have tried uses piezo electric disks. They have a high voltage sensitivity. The disks also seem to be quite good at detecting low frequency sound / air pressure changes; low flying helicopters in particular! I have a twin flask arrangement which I have been doing some initial experiments with. One flask acts as a stable air pressure reservoir and the other as a low pass acoustic filter. I prefer to remove ambient noise as far as possible, rather than detecting it and then filtering the signal. This also stabilises the temperature of the detector disk reasonably well. Reducing ambient wind and other noises is reported to be a major consideration. One of the older types of infrasound array used a large circular pipe connected to a sensor at the centre by several hard radial pipes, typically six to eight. You should be able to use porous hose for the circle and maybe PVC hose / water pipe for the radial arms? This might give better noise cancellation and a higher sensitivity than two folded pipes? A circle of 25 ft radius has a perimeter of about 157 ft. This could give you a collection area of nearly 2,000 sq ft. Air pressure eddies less than this size will tend to cancel out. You might get a hf noise cut-off at about 20 Hz. I note that some of the current CTBT arrays are using solid pipe at the centre of the spokes and porous pipe for remainder. Porous hose is reported to change it's acoustic characteristics with time and it is also sensitive to rain. Is your 1 Hz figure a high frequency cut-off? I have got some characteristics of Validyne sensors somewhere. The low range sensors are from 0.1" water FS upwards, but I don't remember any frequency or noise specifications. I don't know how much they cost, but a Ball Glider Variometer might well offer both price and sensitivity advantages. They use the same principle of pressure sensor, but with a mylar membrane. You can also get low pressure range silicon sensors. Regards, Chris Chapman
In a message dated 05/01/2006 00:40:06 GMT Standard Time, AHrubetz@..... com=20 writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000>
Hi Chris,
    The detector is a Validyne pressure transducer=20 modified by Dr. Chris Haywood at SMU. I don't know what modifications= =20 were made, and have borrowed the detector to see if I could record anythin= g of=20 interest with it. There are 8 inlets into a small volume inlet=20 box. A metal diaphram measures pressure variations differentially wit= h=20 respect to a reference pressure in a larger volume. The bridge=20 circuit electronics is contained within the detector and is powered b= y 12=20 volts furnished by an external power supply located about 50' from the=20 detector. It has an internal 1 Hz low gain cutoff. I have no spe= cs=20 on the unit. I am only using two of the inlets, connected to two 50'=20 porous hoses extended  inline from opposite sides of the detecto= r.=20 Because of space restrictions, the hoses are doubled back on each oth= er=20 at a length of 25'. 
    What type instrument are you using, and have you=20 recorded any quake-related events?
Hi Al,
 
    Lately, I have been mostly occupied with a=20 seismometers for schools project. One of the sensor types that I have tried=20 uses piezo electric disks. They have a high voltage sensitivity.
 
    The disks also seem to be quite good at detecti= ng=20 low frequency sound / air pressure changes; low flying helicopters in=20 particular! I have a twin flask arrangement which I have been doing som= e=20 initial experiments with. One flask acts as a stable air pressure reservoir=20= and=20 the other as a low pass acoustic filter. I prefer to remove ambient noise as= far=20 as possible, rather than detecting it and then filtering the signal. This al= so=20 stabilises the temperature of the detector disk reasonably well. Reducing=20 ambient wind and other noises is reported to be a major=20 consideration.
 
    One of the older types of infrasound array used= a=20 large circular pipe connected to a sensor at the centre by several hard radi= al=20 pipes, typically six to eight. You should be able to use porous hose fo= r=20 the circle and maybe PVC hose / water pipe for the radial arms? This might g= ive=20 better noise cancellation and a higher sensitivity than two folded pipes? A=20 circle of 25 ft radius has a perimeter of about 157 ft. This could give= you=20 a collection area of nearly 2,000 sq ft. Air pressure eddies less than this=20= size=20 will tend to cancel out. You might get a hf noise cut-off at about 20 H= z. I=20 note that some of the current CTBT arrays are using solid pipe at the centre= of=20 the spokes and porous pipe for remainder. Porous hose is reported to change=20= it's=20 acoustic characteristics with time and it is also sensitive to rain.
 
    Is your 1 Hz figure a high frequency cut-off? I= =20 have got some characteristics of Validyne sensors somewhere. The low range=20 sensors are from 0.1" water FS upwards, but I don't remember=20= any=20 frequency or noise specifications. I don't know how much they cost, but a Ba= ll=20 Glider Variometer might well offer both price and sensitivity advantages. Th= ey=20 use the same principle of pressure sensor, but with a mylar membrane. You ca= n=20 also get low pressure range silicon sensors.
 
    Regards,
 
    Chris Chapman
Subject: INFRASOUND From: AHrubetz@....... Date: Wed, 4 Jan 2006 23:24:59 EST Hi Chris, Thanks very much for the interesting information pertaining to the various detectors and Infrasound detector arrays. Unfortunately, I am restricted to a rather narrow outside rectangular area ( about 2' x 25') for my detector and porous hose layout, hence the linearity of the configuration. Yes, it would be ideal to use radial arms and/or a circular configuration to supress ambient noise but I have to work with this restriction, at least for now. I was advised to use a 1 Hz HP filter, and recorded in this mode for about a month before removing the filter. I believe it eliminated too much of the lower frequencies that enriched the Infrasound signal. I have had some good correlation with weather fronts and barograph changes. I also recorded what appeared to be Infrasound correlation with solar radiation storms several months ago, but have not had the time to make further attempts at this or other correlative studies. I will keep you advised if I come up with anything interesting, solar or terrestial! Best regards, Al
Hi Chris,
    Thanks very much for the interesting informa= tion pertaining to the various detectors and Infrasound detector arrays.&nbs= p; Unfortunately, I am restricted to a rather narrow outside rectangular&nbs= p;area ( about 2' x 25') for my detector and porous hose layout, hence=20= the linearity of the configuration.  Yes, it would be ideal to use radi= al arms and/or a circular configuration to supress ambient noise but I have=20= to work with this restriction, at least for now.  I was advised to use=20= a 1 Hz HP filter, and recorded in this mode for about a month before removin= g the filter.  I believe it eliminated too much of the lower frequencie= s that enriched the Infrasound signal.  
     I have had some good correla= tion with weather fronts and barograph changes.  I also recorded w= hat appeared to be Infrasound correlation with solar radiation storms s= everal months ago, but have not had the time to make further attem= pts at this or other correlative studies.  I will keep you advised if I= come up with anything interesting, solar or terrestial!
    Best regards,
    Al 
Subject: Range of 4,5Hz geophone From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sat, 07 Jan 2006 12:37:59 +0000 Hi all What is the estimated range of 4,5Hz Geophone to detect earthquakes, three axis ? Then i am counting in kilometers. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: ian ian@........... Date: Sat, 07 Jan 2006 13:54:23 +0000 if it's any help, I picked up the 3.0 mag quake at Fort William, Scotland on the 10th of December. I'm probably about 150 Km away, see http://www.earthquakes.bgs.ac.uk/recent_events/20051210232129.9.html (I'm just to the right of Edinburgh, having fallen off the map!). I have a single, vertical 4.5 Hz geophone and got a very respectable trace from it. I would agree, though, that life is more "exciting" with a long period device, like a Lehman, unless you live "on top of a volcano", as I used to do. Cheers Ian http://www.iasmith.com/realtime.htm Jón Frímann wrote: >Hi all > >What is the estimated range of 4,5Hz Geophone to detect earthquakes, >three axis ? Then i am counting in kilometers. > >Regards. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: ian ian@........... Date: Sat, 07 Jan 2006 13:54:23 +0000 if it's any help, I picked up the 3.0 mag quake at Fort William, Scotland on the 10th of December. I'm probably about 150 Km away, see http://www.earthquakes.bgs.ac.uk/recent_events/20051210232129.9.html (I'm just to the right of Edinburgh, having fallen off the map!). I have a single, vertical 4.5 Hz geophone and got a very respectable trace from it. I would agree, though, that life is more "exciting" with a long period device, like a Lehman, unless you live "on top of a volcano", as I used to do. Cheers Ian http://www.iasmith.com/realtime.htm Jón Frímann wrote: >Hi all > >What is the estimated range of 4,5Hz Geophone to detect earthquakes, >three axis ? Then i am counting in kilometers. > >Regards. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sat, 07 Jan 2006 14:11:29 +0000 Hi Ian and others. I did ask becose i didn't pickup a 3,5 mag earthquake that did happen yesterday about 100 - 180 Km nne of where i life. You can get more info on that earthquake here > http://hraun.vedur.is/ja/englishweb/eqlist.html the automatic system that i.m.o has marks it as a 3,8Ml in size, the quality was rather poor on the i.m.o system. But for some reasion i didn't pick it up, i might have setup the warning system in winsdr too hig or something in the ground did prevent me from picking it up, but i did change the setting after i did notice this. To prevent me from recording noise, i did set the sla/tla ratio to 8.0, but far as i understand it. That controls the warning levels pickups. The earthquake that where happening yesterday where on the 2 - 4Hz (problay higher) bands, as can be seen here > http://hraun.vedur.is/ja/oroi/hrn.gif there are more stations http://hraun.vedur.is/ja/englishweb/tremor.html here. The noise level in my evroment is not too hig, based on what i have seen the three weeks i have been running the geophone. But i am still learning proplery on this hardware. That is why i will ask questions. However, yesterday was rather windy day and the noise levels where above the usual level. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auction From: Bob Barns royb1@........... Date: Sat, 07 Jan 2006 09:58:11 -0500 Hi gang, Vintage Seismograph Seiscor Telephone Test Set - L@@k! Item number: 6595047948 ends 1/13 Can someone post what this thing is? It looks capable of almost anything?? Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: ian ian@........... Date: Sat, 07 Jan 2006 15:21:39 +0000 Hi, it can also depend on the depth and other factors, whether you pick it up or not. I record my data continuously. Disk space is cheap. I only learned of the Fort William quake about a week after it happened. I went back to the files (I record 30 minutes per file) for the time and date and there it was. Cheers Ian Jón Frímann wrote: >Hi Ian and others. > >I did ask becose i didn't pickup a 3,5 mag earthquake that did happen >yesterday about 100 - 180 Km nne of where i life. You can get more info >on that earthquake here > >http://hraun.vedur.is/ja/englishweb/eqlist.html the automatic system >that i.m.o has marks it as a 3,8Ml in size, the quality was rather poor >on the i.m.o system. But for some reasion i didn't pick it up, i might >have setup the warning system in winsdr too hig or something in the >ground did prevent me from picking it up, but i did change the setting >after i did notice this. To prevent me from recording noise, i did set >the sla/tla ratio to 8.0, but far as i understand it. That controls the >warning levels pickups. > >The earthquake that where happening yesterday where on the 2 - 4Hz >(problay higher) bands, as can be seen here > >http://hraun.vedur.is/ja/oroi/hrn.gif there are more stations >http://hraun.vedur.is/ja/englishweb/tremor.html here. > >The noise level in my evroment is not too hig, based on what i have seen >the three weeks i have been running the geophone. But i am still >learning proplery on this hardware. That is why i will ask questions. >However, yesterday was rather windy day and the noise levels where above >the usual level. > >Regards. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Range of 4,5Hz geophone From: "Steve Hammond" shammon1@............. Date: Sat, 7 Jan 2006 09:59:50 -0800 Jon, My station ID is ATx and I have a lot of geophone data on Larry's system under ATE, ATN and ATX that is from three HS-10 geophones with a gain of 2,100. As a rule, I don't look for event data if the event is less than a 3.0 and more than 200 km away, 4.0 and more than 300 km, 5.0 and more than 400 km. Smaller local events less than 2.0 can be lost in the local noise because I live near the Monterey Bay in Central California. Regards, Steve Hammond PSN San Jose, Aptos, California -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Jón Frímann Sent: Saturday, January 07, 2006 4:38 AM To: PSN-Postlist Subject: Range of 4,5Hz geophone Hi all What is the estimated range of 4,5Hz Geophone to detect earthquakes, three axis ? Then i am counting in kilometers. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Range of 4,5Hz geophone From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sat, 07 Jan 2006 21:02:20 +0000 Hi all I do think i found the source of the problem, i think that the ampling of the psnamp board was too low. I did change it, but i am not sure how much i did change it, it has the jumper on and the gain is from 175 - 1750. I did turn them clockwise and i think the settings now at maximum settings. I see bit more noise then i did before. If the range of a 4,5Hz geophone is up to 640 km max, then i problay will not have problems picking up most small quakes that happen near me, or at least up to 200km away from me. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: ian ian@........... Date: Sun, 08 Jan 2006 12:40:07 +0000 I'm getting an amazing trace on my Lehman of the Greek quake, still in progress. Interestingly, there is a small event on my geophone which seems to co-incide with the P wave. Is this likely? See http://www.iasmith.com/realtime.htm I'm just about to fit a permanent set of heaters in the box. The temporary desk lamp has been great since I put it in, cured the problem completely. I'll have to wait a bit now so as to not disturb the trace in progress.... Ian Smith Jón Frímann wrote: >Hi all > >I do think i found the source of the problem, i think that the ampling >of the psnamp board was too low. I did change it, but i am not sure how >much i did change it, it has the jumper on and the gain is from 175 - >1750. I did turn them clockwise and i think the settings now at maximum >settings. I see bit more noise then i did before. > >If the range of a 4,5Hz geophone is up to 640 km max, then i problay >will not have problems picking up most small quakes that happen near me, >or at least up to 200km away from me. > >Regards. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sun, 08 Jan 2006 16:27:11 +0000 Hi Ian and others. I didn't recored or see this earthquake on my geophone, something probaly shatters the wave before it reaches me or trims it down below the local noise. I know it was detected by the i.m.o siesmonitors. I have alot bigger amplitude on my geophone then before, so i hope to pickup earthquakes when they happen. I now record alot of noise, for instance i see alot more wind being picked up by my geophone, even if it is inside and well isolated. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: John or Jan Lahr JohnJan@........ Date: Sun, 08 Jan 2006 08:32:57 -0800 Hi Ian, It's possible that the small event was triggered by the arriving seismic waves, although this usually occurs later when the surface waves are arriving. See, for example, this page by USGS seismologist Andy Michael: http://quake.wr.usgs.gov/~michael/surprises.html This has been observed in may volcanic and hydrothermal areas, where presumable there are some "spots" that are so close to failure that the added strain produced by the waves of a distant earthquake can set some of them off. Andy's main page is: http://quake.wr.usgs.gov/~michael/ This "event" is more likely just the high frequency component of the P wave. It's hard to tell from the seismograms, but if it starts at exactly the same time as P on the Lehman, then it's probably not a triggered event. Cheers, John At 04:40 AM 1/8/2006, you wrote: >I'm getting an amazing trace on my Lehman of the Greek quake, still >in progress. Interestingly, there is a small event on my geophone >which seems to co-incide with the P wave. Is this likely? See >http://www.iasmith.com/realtime.htm > >I'm just about to fit a permanent set of heaters in the box. The >temporary desk lamp has been great since I put it in, cured the >problem completely. I'll have to wait a bit now so as to not >disturb the trace in progress.... > >Ian Smith __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: ian ian@........... Date: Sun, 08 Jan 2006 16:39:27 +0000 Hi, I wouldn't really expect to pick up a quake from Greece with a geophone at the distance you are at. You really have to have a longer period device to detect it. I'm not sure if the spike on my geophone was the P wave or just something local. Either way, the geophone spike was brief compared to the 90 minutes or so that the quake grumbled on for. Maybe you should have a go at making something like a Lehman. They're not too difficult and you probably have a spare channel on your amp and A/D. I've spent the afternoon replacing the desk lamp in the enclosure with 3 car lights. I'm starting off by feeding them 5 volts from an old PC power supply. If that isn't warm enough then I'll switch to 12 volts. Thanks to Chris Chapman for pointing this out, it's made a huge difference. Cheers Ian Jón Frímann wrote: >Hi Ian and others. > >I didn't recored or see this earthquake on my geophone, something >probaly shatters the wave before it reaches me or trims it down below >the local noise. I know it was detected by the i.m.o siesmonitors. I >have alot bigger amplitude on my geophone then before, so i hope to >pickup earthquakes when they happen. I now record alot of noise, for >instance i see alot more wind being picked up by my geophone, even if it >is inside and well isolated. > >Regards. > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: The earthquake in Greece From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Sun, 08 Jan 2006 16:45:46 +0000 Hi all John, thanks for mension this. Becose there has been a increase in earthquakes in Silicy, Italy after the Greece earthquake. It did start about three hours after the main quake in Greece. You can get the earthquake data here. http://www.emsc-csem.org/cgi-bin/QDM_all.sh?1 Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: ian ian@........... Date: Sun, 08 Jan 2006 16:48:07 +0000 Hi, thanks for the links. Interesting thought. If the BGS was working I'd be able to check if it was real or local. BGS sensors have been off since the 24th of December, outrageous and embarrassing. Presumably Monday may bring some hope. I'm tempted to email a complaint to them (it's my taxes!). Thanks Ian John or Jan Lahr wrote: > Hi Ian, > > It's possible that the small event was triggered by the arriving > seismic waves, although this usually occurs later when the surface > waves are arriving. See, for example, this page by USGS seismologist > Andy Michael: > http://quake.wr.usgs.gov/~michael/surprises.html > This has been observed in may volcanic and hydrothermal areas, where > presumable there are some "spots" that are so close to failure that > the added strain produced by the waves of a distant earthquake can set > some of them off. > > Andy's main page is: > http://quake.wr.usgs.gov/~michael/ > > This "event" is more likely just the high frequency component of the P > wave. It's hard to tell from the seismograms, but if it starts at > exactly the same time as P on the Lehman, then it's probably not a > triggered event. > > Cheers, > John > > > At 04:40 AM 1/8/2006, you wrote: > >> I'm getting an amazing trace on my Lehman of the Greek quake, still >> in progress. Interestingly, there is a small event on my geophone >> which seems to co-incide with the P wave. Is this likely? See >> http://www.iasmith.com/realtime.htm >> >> I'm just about to fit a permanent set of heaters in the box. The >> temporary desk lamp has been great since I put it in, cured the >> problem completely. I'll have to wait a bit now so as to not disturb >> the trace in progress.... >> >> Ian Smith > > > > __________________________________________________________ > > 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: Range of 4,5Hz geophone,Greek quake From: "Thomas Dick" dickthomas01@............. Date: Sun, 8 Jan 2006 11:13:28 -0600 My vertical geophone detected this quake. I am 82 degrees away. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Range of 4,5Hz geophone From: ChrisAtUpw@....... Date: Sun, 8 Jan 2006 13:29:59 EST In a message dated 08/01/2006, ian@........... writes: I've spent the afternoon replacing the desk lamp in the enclosure with 3 car lights. I'm starting off by feeding them 5 volts from an old PC power supply. If that isn't warm enough then I'll switch to 12 volts. Hi Ian, There are two problems with using light bulbs. You need to run them at 3/4 the rated voltage to get a very long life from them and the glass envelopes need to be kept cool. If the glass gets too hot, oxygen may diffuse through it and shorten the filament life. The other problem is that insects, spiders and small animals are attracted to a warmed environment, particularly if it is also illuminated. Power resistors with an Al case which can be bolted onto an earthed Al top plate in the enclosure and provided with soldered connections are likely to give the most satisfactory permanent solution. Farnell and RS sell them. Regards, Chris Chapman
In a message dated 08/01/2006, ian@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I've=20 spent the afternoon replacing the desk lamp in the enclosure with 3
ca= r=20 lights. I'm starting off by feeding them 5 volts from an old PC
p= ower=20 supply. If that isn't warm enough then I'll switch to 12 volts. =20
Hi Ian,
 
    There are two problems with using light bulbs.=20= You=20 need to run them at 3/4 the rated voltage to get a very long life from them=20= and=20 the glass envelopes need to be kept cool. If the glass gets too hot, oxygen=20= may=20 diffuse through it and shorten the filament life. The other problem is that=20 insects, spiders and small animals are attracted to a warmed=20 environment, particularly if it is also=20 illuminated.     
    Power resistors with an Al case which can be bo= lted=20 onto an earthed Al top plate in the enclosure and provided with soldered=20 connections are likely to give the most satisfactory permanent solution= ..=20 Farnell and RS sell them.   
 
    Regards,
 
    Chris Chapman
Subject: Re: Range of 4,5Hz geophone From: ian ian@........... Date: Sun, 08 Jan 2006 18:58:50 +0000 Hi, thanks for the warnings. As always, I've taken a short cut (lack of time). I also had to get the desk lamp out by today as my family return tomorrow and will want the desk lamp back(!) and wouldn't want a mains lead stretching across the garden/back yard. It was nice and cosy inside the box when I opened it up, so the thermal insulation isn't too bad. It was around 0C outside at the time. I ripped out the flasher, stop and tail light string from our old Honda and attached that to the inside ceiling of the enclosure. I'm only sending 5 volts dc to them (down 30m of mains lead) so they don't get very hot at all, just a warming glow. Unfortunately I won't have much more time until the summer. So I'll have to wait until then before changing over to resistors. Unless of course it starts going bump in the night! Cheers Ian ChrisAtUpw@....... wrote: > In a message dated 08/01/2006, ian@........... writes: > > I've spent the afternoon replacing the desk lamp in the enclosure > with 3 > car lights. I'm starting off by feeding them 5 volts from an old PC > power supply. If that isn't warm enough then I'll switch to 12 > volts. > > Hi Ian, > > There are two problems with using light bulbs. You need to run > them at 3/4 the rated voltage to get a very long life from them and > the glass envelopes need to be kept cool. If the glass gets too hot, > oxygen may diffuse through it and shorten the filament life. The other > problem is that insects, spiders and small animals are attracted to a > warmed environment, particularly if it is also illuminated. > Power resistors with an Al case which can be bolted onto an > earthed Al top plate in the enclosure and provided with soldered > connections are likely to give the most satisfactory permanent > solution. Farnell and RS sell them. > > Regards, > > Chris Chapman Hi,

thanks for the warnings. As always, I've taken a short cut (lack of time).  I also had to get the desk lamp out by today as my family return tomorrow and will want the desk lamp back(!) and wouldn't want a mains lead stretching across the garden/back yard.  It was nice and cosy inside the box when I opened it up, so the thermal insulation isn't too bad.  It was around 0C outside at the time.

I ripped out the flasher, stop and tail light string from our old Honda and attached that to the inside ceiling of the enclosure.  I'm only sending 5 volts dc to them (down 30m of mains lead) so they don't get very hot at all, just a warming glow.  Unfortunately I won't have much more time until the summer.  So I'll have to wait until then before changing over to resistors.  Unless of course it starts going bump in the night!

Cheers

Ian

ChrisAtUpw@....... wrote:
In a message dated 08/01/2006, ian@........... writes:
I've spent the afternoon replacing the desk lamp in the enclosure with 3
car lights. I'm starting off by feeding them 5 volts from an old PC
power supply. If that isn't warm enough then I'll switch to 12 volts. 
Hi Ian,
 
    There are two problems with using light bulbs. You need to run them at 3/4 the rated voltage to get a very long life from them and the glass envelopes need to be kept cool. If the glass gets too hot, oxygen may diffuse through it and shorten the filament life. The other problem is that insects, spiders and small animals are attracted to a warmed environment, particularly if it is also illuminated.     
    Power resistors with an Al case which can be bolted onto an earthed Al top plate in the enclosure and provided with soldered connections are likely to give the most satisfactory permanent solution. Farnell and RS sell them.   
 
    Regards,
 
    Chris Chapman
Subject: Re: Range of 4,5Hz geophone From: "Geoff" gmvoeth@........... Date: Sun, 8 Jan 2006 13:05:42 -0700 I understand the physics of wave propagation through water or ground or anything allows for shadow areas where there is little or no energy. It seems reasonable to assume such shadow areas can affect small areas closer to the event and not just 103 or so degrees away. maybe you were just in one of these shadow zones ??? > I didn't recored or see this earthquake on my geophone, something > probaly shatters the wave before it reaches me or trims it down below > the local noise. I know it was detected by the i.m.o siesmonitors. I But then I am no geophysicist, the person most likely to know. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Online seismonitor graphs are offline From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Mon, 09 Jan 2006 01:11:38 +0000 Hi all. My online seismonitors graphs are currently offline due to technical problems. I hope to have them back online tomorrow, but i will have to move them to my own server at my home, so the address will change. I will setup a forward page also on the old place tomorrow (where my page is), so you will get redireced to the new location automaticlly. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Updated link From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Mon, 09 Jan 2006 13:08:21 +0000 Hi all I finally got my seismographs online agen (hopefully). There has been minor updated in the link. The current link is http://www.simnet.is/jonfr500/earthquake/ and that this is a backup link number two, the main backup link is this one http://earthquake.homeip.net/~jonfr/ , the main link is going to be http://www.jonfr.com/earthquake/ But at current time i am having problems peforming a update to that location. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Earthquake in the North Atlantic Ocen, 5,3mb From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Mon, 09 Jan 2006 17:11:53 +0000 Hi all Today (9th Jan, 2006) there was a earthquake of 5.3 mb in the North Atlantic Ocen, the depth was 2 km. There are more info at esmc-cmes.org and here http://www.emsc-csem.org/cgi-bin/QDM_link_content.sh?HB644&CSEM The link might stop working anytime. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: $200 microbarograph first light From: "David Saum" DSaum@............ Date: Mon, 9 Jan 2006 15:08:10 -0500 I finally got my $200 home-brew microbarograph running yesterday, and here are some pictures: Here is last night's data logged and plotted hourly with the seismic freeware AMASEIS. Time is GMT. Bandpass 0.01 Hz to 4.5 Hz. http://www.infiltec.com/Infrasound@................. The microbarograph was in a cooler, outside on the 4th floor deck of my condo, with no spatial wind averaging array. I am about 10 miles from Washington Reagan airport, and they reported 9-15mph winds, so the peaks are probably wind and not seismic events, nuclear tests, meteors, etc. :( Here is some fine structure of one of last night's events: http://www.infiltec.com/Infrasound@................. The adc pressure resolution is about 0.004 Pa, so a 200 adc count peak is about 0.8 Pa. AMASEIS allows you to block any time segment and examine it in detail, including fourier transform and bandpass filtering. Exterior of microbarograph with serial cable: http://www.infiltec.com/Infrasound@................. Interior of microbarograph: http://www.infiltec.com/Infrasound@................. PCB removed from box http://www.infiltec.com/Infrasound@................. PCB and high-pass pneumatic filter removed from box: http://www.infiltec.com/Infrasound@................. System specs: System Bandpass: 0.01 to 4 Hz. High-Pass filter: ~100 sec or 0.01 Hz using volume/capillary tube. Low pass filter: 4 Hz anti-alias, 8 pole Bessel filter (MAX4701) Differential pressure sensor: silicon, bridge type, 1"wc (DUXL01D) Pres Resolution: ~0.004 Pa - possibly lower depending offsets Range: +/- 120 Pa (32768 times pressure resolution) Amp: instrumentation,1000x,single supply,micropower,RTR out(INA122P) Power: ~2ma 5VDC, derived from PC serial port, no exernal power supply Regulator: 5VDC, low dropout micropower, precision (LP2950-5.0) Amplifer Reference Voltage: 2.5VDC fixed, precision reference (LT1004-2.5) Microprocessor: 4mhz, onboard 16 bit ADC and serial I/O (PIC14000) Firmware: ADC sampling at ~35 SPS, zero drift tracking ~5 min TC. Enclosure: diecast aluminum box for shielding (Hammond 1590P) Serial Out: RS232, 9600 baud, 8N1, ascii records, -32767 to +32767 Wind Spatial Averaging: array of micro-perforated garden tubing Data Log/Display: freeware PC AMASEIS seismic log/analysis software Improvements?: Offset voltages in the instrumentation amp and pressure sensor seem to limit the maximum gain. I may try a variable amp reference voltage to eliminate these offsets. I bought some pressure transmitters from eBay to see if their noise levels are lower: an MKS Baratron 223B and an Ashcroft XLDP. Unfortunately these transmitters use a lot more power and voltage than I can steal from the PC serial port. Kits: If there is some interest I will offer a kit for this microbarograph. It would be similar to my seismometer kit that is described below, including step-by-step building instructions : http://www.infiltec.com/seismo/infkqm10.htm The seismometer kit was recently built by an 8th grader for her science project. Dave __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: $200 microbarograph first light From: "John D Nelson" jnelson@................. Date: Mon, 9 Jan 2006 14:19:19 -0600 I would certainly be interested in seeing a kit offered, or at least the circuit board. John Nelson -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of David Saum Sent: Monday, January 09, 2006 2:08 PM To: Undisclosed-Recipient:; Subject: $200 microbarograph first light I finally got my $200 home-brew microbarograph running yesterday, and here are some pictures: Here is last night's data logged and plotted hourly with the seismic freeware AMASEIS. Time is GMT. Bandpass 0.01 Hz to 4.5 Hz. http://www.infiltec.com/Infrasound@................. The microbarograph was in a cooler, outside on the 4th=20 floor deck of my condo, with no spatial wind averaging array.=20 I am about 10 miles from Washington Reagan airport, and they reported 9-15mph winds, so the peaks are probably wind and not seismic events, nuclear tests, meteors, etc. :( Here is some fine structure of one of last night's events: http://www.infiltec.com/Infrasound@................. The adc pressure resolution is about 0.004 Pa, so a 200 adc=20 count peak is about 0.8 Pa. AMASEIS allows you to block any time segment and examine it in detail, including fourier transform and bandpass filtering. Exterior of microbarograph with serial cable: http://www.infiltec.com/Infrasound@................. Interior of microbarograph: http://www.infiltec.com/Infrasound@................. PCB removed from box http://www.infiltec.com/Infrasound@................. PCB and high-pass pneumatic filter removed from box: http://www.infiltec.com/Infrasound@................. System specs:=20 System Bandpass: 0.01 to 4 Hz. High-Pass filter: ~100 sec or 0.01 Hz using volume/capillary tube. Low pass filter: 4 Hz anti-alias, 8 pole Bessel filter (MAX4701) Differential pressure sensor: silicon, bridge type, 1"wc (DUXL01D) Pres Resolution: ~0.004 Pa - possibly lower depending offsets Range: +/- 120 Pa (32768 times pressure resolution) Amp: instrumentation,1000x,single supply,micropower,RTR out(INA122P)=20 Power: ~2ma 5VDC, derived from PC serial port, no exernal power supply Regulator: 5VDC, low dropout micropower, precision (LP2950-5.0) =20 Amplifer Reference Voltage: 2.5VDC fixed, precision reference (LT1004-2.5) Microprocessor: 4mhz, onboard 16 bit ADC and serial I/O (PIC14000) Firmware: ADC sampling at ~35 SPS, zero drift tracking ~5 min TC. Enclosure: diecast aluminum box for shielding (Hammond 1590P) Serial Out: RS232, 9600 baud, 8N1, ascii records, -32767 to +32767 Wind Spatial Averaging: array of micro-perforated garden tubing=20 Data Log/Display: freeware PC AMASEIS seismic log/analysis software Improvements?: Offset voltages in the instrumentation amp and pressure sensor seem to limit the maximum gain. I may try a variable amp reference voltage to eliminate these offsets. I bought some pressure transmitters from eBay to see if their noise levels are lower: an MKS Baratron 223B and an Ashcroft XLDP. Unfortunately these transmitters use a lot more power and voltage than I can steal from the PC serial port. Kits: If there is some interest I will offer a kit for this microbarograph. It would be similar to my seismometer kit that is described below, including step-by-step building instructions : http://www.infiltec.com/seismo/infkqm10.htm The seismometer kit was recently built by an 8th grader for her science project. Dave=20 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: $200 microbarograph first light From: "James Hannon" jmhannon@......... Date: Mon, 9 Jan 106 14:26:33 CST Dave, Looks real nice. I was wondering about the high pass filter. The capillary tube seems large. Did you arrive at the volume/ tube dia/ length by calculation or experiment? Do you have any data on these parameters vs response? Jim Hannon -- Jim Hannon http://www.fmtcs.com/web/jmhannon/ 42,11.90N,91,39.26W WB0TXL -- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Recorded two 3 ricther scale earthquakes From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Tue, 10 Jan 2006 02:09:29 +0000 Hi all Thanks to comment on how to increase the amptiude i did finally record earthquakes. This earthquakes are two, with just a few seconds time between them. The size according to i.m.o is 3,0Ml and 3,4Ml. The range from my station is about ~220 km. Below are gif image of the earthquake and the psn file. http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn.gif http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: $200 microbarograph first light From: ChrisAtUpw@....... Date: Mon, 9 Jan 2006 22:56:18 EST In a message dated 09/01/2006, DSaum@............ writes: Improvements? Offset voltages in the instrumentation amp and pressure sensor seem to limit the maximum gain. If you use a low noise differential input amplifier, but keep the gain at a level at which it does not saturate, you can add a high pass filter and then additional amplification and filtering. It can be a bit difficult to zero the sensor without increasing it's noise. In the equipment shown, the reference pressure is a very small volume connected to atmosphere with a leak tube. The temperature of the reference volume usually needs to be stabilised, to reduce ambient drift, especially when using a fairly long time constant, like 100 sec. A half pint thermos flask filled with the lightest grade of polyurethane foam makes quite a good reference. This allows the pressure sensing to be ~isothermal rather than semi adiabatic and increases the sensitivity. The ambient thermal response time of an empty flask is usually over 30 mins. The 'thermal mass' can be increased by adding candle wax inside the flask. The sensor shown will pick up wide band ambient noise from the wind, passing aircraft, helicopters, vehicles..... Unless you want to observe these sorts of signal, you can use a single stage pneumatic low pass filter, with a leak tube and a reference volume, to reduce the input noise. This may be quite helpful in keeping the output 'on scale', particularly in very windy / noisy conditions. Wind noise can be reduced by using a large sensor array of porous irrigation hose. This may be protected from rain to keep the acoustic properties fairly constant. A large circle of hose connected to a sensor at the centre by four to eight hard wall connecting tubes has been used for infrasound arrays, with diameters up to several hundred feet. Radial spokes of porous hose are also used, usually connected to the sensor with lengths of solid tube. It is also possible to use a single sensor head with a multi hole entry in between horizontal disks. This can significantly reduce the wind noise. Buildings, isolated trees, water towers, pylons etc will all have downwind vortices associated with them which can greatly increase the input signal amplitude at a 'miss-placed' sensor, usually to over twice the crosswind dimension. The turbulence generated by a structure like a wall or a hedge may be detected at distances over 50x the height downwind. Regards, Chris Chapman
In a message dated 09/01/2006, DSaum@............ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Improvements? Offset voltages in the instrumentation amp and=20 pressure
sensor seem to limit the maximum=20 gain. 
    If you use a low noise differential input=20 amplifier, but keep the gain at a level at which it does not saturate, you c= an=20 add a high pass filter and then additional amplification and filtering. = ;It=20 can be a bit difficult to zero the sensor without increasing it's=20 noise. 
 
    In the equipment shown, the reference pressure=20= is a=20 very small volume connected to atmosphere with a leak tube. The tempera= ture=20 of the reference volume usually needs to be stabilised, to reduce ambient dr= ift,=20 especially when using a fairly long time constant, like 100 sec. A half= =20 pint thermos flask filled with the lightest grade of polyurethane foam makes= =20 quite a good reference. This allows the pressure sensing to be ~isother= mal=20 rather than semi adiabatic and increases the sensitivity. The ambient therma= l=20 response time of an empty flask is usually over 30 mins. The 'thermal m= ass'=20 can be increased by adding candle wax inside the flask.
 
    The sensor shown will pick up wide band ambient= =20 noise from the wind, passing aircraft, helicopters, vehicles..... Unless you= =20 want to observe these sorts of signal, you can use a single stage pneumatic=20= low=20 pass filter, with a leak tube and a reference volume, to reduce the inp= ut=20 noise. This may be quite helpful in keeping the output 'on scale', particula= rly=20 in very windy / noisy conditions. 
 
    Wind noise can be reduced by using a large sens= or=20 array of porous irrigation hose. This may be protected from rain to keep the= =20 acoustic properties fairly constant. A large circle of hose connected to a=20 sensor at the centre by four to eight hard wall connecting tubes has be= en=20 used for infrasound arrays, with diameters up to several hundred feet. Radia= l=20 spokes of porous hose are also used, usually connected to the sensor with=20 lengths of solid tube.
 
    It is also possible to use a single sensor head= =20 with a multi hole entry in between horizontal disks. This can significa= ntly=20 reduce the wind noise. Buildings, isolated trees, water towers, pylons=20= etc=20 will all have downwind vortices associated with them which can greatly incre= ase=20 the input signal amplitude at a 'miss-placed' sensor, usually to over twice=20= the=20 crosswind dimension. The turbulence generated by a structure like a wal= l or=20 a hedge may be detected at distances over 50x the height downwind.
 
    Regards,
 
    Chris Chapman
Subject: ebay auction From: Bob Barns royb1@........... Date: Tue, 10 Jan 2006 10:38:15 -0500 GeoSonics SSU Micro Seismograph Earthquake System Unit Item number: 7579963838 ends 1/16 Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Locating P and S wave, suggestions needed From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@......... Date: Tue, 10 Jan 2006 17:53:25 +0000 Hi all As I did say in my early post today, I did record a earthquake at 00:25 today. The earthquake mag was 3,0 on the ricther scale according to the icelandic met office. My problem is this that i don't think i have found the p and s wave properly, since this earthquake wave has two spikes, not one. I did think that i had correctly located the p and s waves, but based on the wave form I am not totally sure. Here is the gif file and the psn file of the recording. http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn.gif http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn (p and s markers are not set in this psn file) Here is a picture of the earthquake with the p and s markers as i did set them. http://alvaran.com/forum/index.php?act=Attach&type=post&id=11 If nothing else, I welcome suggestions on this matter. Regards. -- Jón Frímann Jónsson http://www.jonfr.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: $200 microbarograph first light From: ChrisAtUpw@....... Date: Tue, 10 Jan 2006 21:49:34 EST In a message dated 09/01/2006, DSaum@............ writes: System Bandpass: 0.01 to 4 Hz. High-Pass filter: ~100 sec or 0.01 Hz using volume/capillary tube. Low pass filter: 4 Hz anti-alias, 8 pole Bessel filter (MAX4701) This gives a drop of 40 dB at 4 Hz, an average signal delay of 0.2 sec and 0.35 sec peak. Differential pressure sensor: silicon, bridge type, 1"wc (DUXL01D) Pres Resolution: ~0.004 Pa - possibly lower depending offsets Range: +/- 120 Pa (32768 times pressure resolution) For a 5 V supply, this sensor has an output of 6 mV per inch water and a span of 6 mV. You might do better with a DUXL05D. This has an output of 4.5 mV per inch water and a span of 22.5 mV. 1" water gauge corresponds to a pitot speed of about 45 mph. This does not leave much, if any, safety margin for storm conditions. Amp: instrumentation,1000x,single supply,micropower,RTR out(INA122P) While the INA122 has rail to rail output, it also has a 0.1 to 10 Hz noise of 2 micro V pp. This is poor in comparison with an INA118 which has a noise level of 0.28 micro V pp - roughly 1/7th. There are other low noise opamps available. Power: ~2ma 5VDC, derived from PC serial port, no exernal power supply Regulator: 5VDC, low dropout micropower, precision (LP2950-5.0) Firmware: ADC sampling at ~35 SPS, zero drift tracking ~5 min TC. Serial Out: RS232, 9600 baud, 8N1, ascii records, -32767 to +32767 Wind Spatial Averaging: array of micro-perforated garden tubing Data Log/Display: freeware PC AMASEIS seismic log/analysis software Improvements? Offset voltages in the instrumentation amp and pressure sensor seem to limit the maximum gain. I may try a variable amp reference voltage to eliminate these offsets. Use the average signal level as your zero? Regards, Chris Chapman
In a message dated 09/01/2006, DSaum@............ writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>System=20 Bandpass: 0.01 to 4 Hz.
High-Pass filter: ~100 sec or 0.01 Hz using=20 volume/capillary tube.
Low pass filter: 4 Hz anti-alias, 8 pole Bessel=20 filter (MAX4701)
    This gives a drop of 40 dB at 4 Hz, an average=20 signal delay of 0.2 sec and 0.35 sec peak.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>Differential pressure sensor: silicon, bridge type, 1"wc=20 (DUXL01D)
Pres Resolution: ~0.004 Pa - possibly lower depending=20 offsets
Range: +/- 120 Pa (32768 times pressure=20 resolution)
    For a 5 V supply, this sensor has an output of=20= 6 mV=20 per inch water and a span of 6 mV. You might do better with a DUXL05D.=20= This=20 has an output of 4.5 mV per inch water and a span of 22.5 mV.
 
    1" water gauge corresponds to a pitot speed of=20 about 45 mph. This does not leave much, if any, safety margin for storm= =20 conditions.

Amp: instrumentation,1000x,single supply,micropower,RTR out(INA= 122P)=20
 
    While the INA122 has rail to rail output, it al= so=20 has a 0.1 to 10 Hz noise of 2 micro V pp. This is poor in comparison with an= =20 INA118 which has a noise level of 0.28 micro V pp - roughly 1/7th. There are= =20 other low noise opamps available.

Power: ~2ma 5VDC, derived from PC serial port, no exernal power=20 supply
Regulator: 5VDC, low dropout micropower, precision (LP2950-5.0)&nb= sp;=20
Firmware: ADC sampling at ~35 SPS, zero drift tracking ~5 min TC.
Ser= ial=20 Out: RS232, 9600 baud, 8N1, ascii records, -32767 to +32767
Wind Spatial=20 Averaging: array of micro-perforated garden tubing
Data Log/Display:=20 freeware PC AMASEIS seismic log/analysis software

Improvements? Offse= t=20 voltages in the instrumentation amp and pressure
sensor seem to limit the= =20 maximum gain.  I may try a variable amp reference
voltage to elimina= te=20 these offsets.
 
    Use the average signal level as your=20 zero?
 
    Regards,
 
    Chris Chapman
 
Subject: Re: Locating P and S wave, suggestions needed From: Paul elegant_dice@......... Date: Wed, 11 Jan 2006 09:44:25 +0800 According to my friend, he reckons they look good. Your S looks good to him, but your P could be moved to coincide with the peak of the first pulse, it seems to be a few samples earlier than the peak. I'm new at this myself, so I'd like to hear some feedback too Jón Frímann wrote: > Hi all > > As I did say in my early post today, I did record a earthquake at 00:25 > today. The earthquake mag was 3,0 on the ricther scale according to the > icelandic met office. My problem is this that i don't think i have found > the p and s wave properly, since this earthquake wave has two spikes, > not one. I did think that i had correctly located the p and s waves, but > based on the wave form I am not totally sure. > > Here is the gif file and the psn file of the recording. > http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn.gif > http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn > (p and s markers are not set in this psn file) > > Here is a picture of the earthquake with the p and s markers as i did > set them. > http://alvaran.com/forum/index.php?act=Attach&type=post&id=11 > > If nothing else, I welcome suggestions on this matter. > > Regards. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Locating P and S wave, suggestions needed From: "Bob Hancock" carpediem1@......... Date: Tue, 10 Jan 2006 21:40:09 -0700 I downloaded the file and then looked at it with the FFT option in = WinQuake. I tried several different filtering options and then settled on = filtering out all data with a frequency longer than 1 hz. I was unable to see anything that looked like an earthquake in the longer frequencies. This appears to be two separate earthquakes such as a primary event and aftershock, rather than a P wave and S wave. In addition, based upon = the higher frequencies of both events, they are relatively close to the = station, although I would not want to hazard a guess at distance. I have noticed similar frequencies from nearby events both in New Jersey where I used = to live and now in Arizona. =20 The initial direction of what I perceived as the P wave is visible and = moves up on both events. As I see it, the first event occurred at 25:53.270 = and the amplitude on the P wave was 20.3. The second event occurred at 26:13.120, and the amplitude on the P wave was 34.6. This all becomes visible when you filter out the lower frequency data, = and expand the X axis to 10 seconds. However, if an expert has a better answer, I will bow to them. Bob Hancock Three Points, AZ -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Paul Sent: Tuesday, January 10, 2006 18:44 To: psn-l@.............. Subject: Re: Locating P and S wave, suggestions needed According to my friend, he reckons they look good. Your S looks good to = him, but your P could be moved to coincide with the peak of the first=20 pulse, it seems to be a few samples earlier than the peak. I'm new at this myself, so I'd like to hear some feedback too J=F3n Fr=EDmann wrote: > Hi all >=20 > As I did say in my early post today, I did record a earthquake at = 00:25 > today. The earthquake mag was 3,0 on the ricther scale according to = the > icelandic met office. My problem is this that i don't think i have = found > the p and s wave properly, since this earthquake wave has two spikes, > not one. I did think that i had correctly located the p and s waves, = but > based on the wave form I am not totally sure. >=20 > Here is the gif file and the psn file of the recording. > http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn.g= if > = http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn > (p and s markers are not set in this psn file) >=20 > Here is a picture of the earthquake with the p and s markers as i did > set them. > http://alvaran.com/forum/index.php?act=3DAttach&type=3Dpost&id=3D11 >=20 > If nothing else, I welcome suggestions on this matter. >=20 > Regards. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Locating P and S wave, suggestions needed From: John or Jan Lahr JohnJan@........ Date: Tue, 10 Jan 2006 21:01:36 -0800 Hi J=F3n, To get better resolution in time, change the time=20 window (x scale) to 40 seconds. Then use the Display/Modify system to enter the=20 known location, origin time, and magnitude from=20 the Iceland network (http://hraun.vedur.is/ja/englishweb/eqlist.html). Click on the Loc button and the P and S markers=20 will be positioned automatically. When I did=20 this they were close to the start of the phases,=20 but a one or two seconds late. This could mean=20 that your clock is a few seconds fast, or that=20 the velocity model does not fit exactly for Iceland. When I position the P and S markers, the implied=20 distance is 162 km, whereas the computed distance=20 is 166 km. This is pretty close. I think you recorded the 3.4 event rather than=20 the 3.0 event, but it can be hard to untangle=20 events that are this close together in space and time. 20= 06-01-1000:25:26,563,964-21,8541,13,490,03=20 5,1 kmSof Helgafell 20= 06-01-1000:25:24,963,955-22,1133,23,090,05=20 7,9 kmNNWof Kr=EDsuv=EDk I posted my WinQuake windows showing the way I would pick this earthquake= here: http://jclahr.com/science/psn/misc/jon.html Cheers, John At 09:53 AM 1/10/2006, you wrote: >Hi all > >As I did say in my early post today, I did record a earthquake at 00:25 >today. The earthquake mag was 3,0 on the ricther scale according to the >icelandic met office. My problem is this that i don't think i have found >the p and s wave properly, since this earthquake wave has two spikes, >not one. I did think that i had correctly located the p and s waves, but >based on the wave form I am not totally sure. > >Here is the gif file and the psn file of the recording. >http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn.gif >http://www.simnet.is/jonfr500/earthquake/winquake/060110.002424.ch1.psn >(p and s markers are not set in this psn file) > >Here is a picture of the earthquake with the p and s markers as i did >set them. >http://alvaran.com/forum/index.php?act=3DAttach&type=3Dpost&id=3D11 > >If nothing else, I welcome suggestions on this matter. > >Regards. >-- >J=F3n Fr=EDmann J=F3nsson >http://www.jonfr.com > >__________________________________________________________ > >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. ##################################/ John C. Lahr #################################/ Emeritus Seismologist ################################/ U.S. Geological Survey =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D/ Geologic Hazards Team ##############################/ Golden, Colorado #############################//############################## ############################//############################### PO Box 548 /################################ Corvallis, Oregon 97339 /################################## Phone: (541) 758-2699 /=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Cell: (541) 740-4844 /################################### Fax: (928) 569-0113 /################################## jjpub@........ /#################################### http://jclahr.com/science/ __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Locating P and S wave, suggestions needed From: John or Jan Lahr JohnJan@........ Date: Tue, 10 Jan 2006 21:08:42 -0800 Bob may be right about this being two events. As soon as there is another 3.5 event within 175 km of Jon's station, it will be clear if he is able to see it clearly. If not, then that would argue for the two-event interpretation. The separation of the two phases is very close to what would be expected for the S-P interval from the distant events, so that argues for my interpretation. John At 08:40 PM 1/10/2006, you wrote: >This appears to be two separate earthquakes such as a primary event and >aftershock, rather than a P wave and S wave. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Locating P and S wave, suggestions needed From: =?ISO-8859-1?Q?J=F3n_Fr=EDman