Author Topic: Seismic Sensors  (Read 7532 times)

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Offline radioactiveTopic starter

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Seismic Sensors
« on: January 05, 2019, 02:51:47 am »
I've been thinking it would be kind of fun to stick a seismometer out under the lawn somewhere around the house and log the data.  I've looked briefly on ebay and search engines for sensors and nothing really stuck out.  Anybody here done this just for fun?  Would love to hear about your experiences and advice on the sensors.
 

Offline boB

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Re: Seismic Sensors
« Reply #1 on: January 05, 2019, 03:03:05 am »
You might want to try adding strain gage to your search.  I think that's what they use for seismographs mostly.

https://engfac.cooper.edu/pages/tzavelis/uploads/Strain-Gage%20instrumentation0.pdf
K7IQ
 

Offline EEVblog

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Re: Seismic Sensors
« Reply #2 on: January 05, 2019, 05:29:25 am »
« Last Edit: January 05, 2019, 05:31:05 am by EEVblog »
 
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Offline coppercone2

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Re: Seismic Sensors
« Reply #3 on: January 05, 2019, 11:01:54 am »
if you were to do this in a slightly more urban then suburban area with lots of rock/elevation, where you live on a hill, would you be able to get useful seismic data or would it be completely polluted by cars and roads/
 

Offline EEVblog

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Re: Seismic Sensors
« Reply #4 on: January 05, 2019, 01:10:15 pm »
if you were to do this in a slightly more urban then suburban area with lots of rock/elevation, where you live on a hill, would you be able to get useful seismic data or would it be completely polluted by cars and roads/

I used to work at the largest seismic water tank in the southern hemisphere, and we often had to schedule tests in the middle of night and to avoid passing trains many km away. Passing trucks were also a pain.
And that was with a properly vibration isolated tank (no such thing as infinitive attenuation).
 

Offline coppercone2

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Re: Seismic Sensors
« Reply #5 on: January 05, 2019, 02:03:57 pm »
does the structure of the land matter. i live in an area littered with lots of granite.

i always thought about seismic sensors and magnetic earth antennas.

there is a highway some one point five miles away or so, and train tracks near the same location. i am maybe fifty or more feet elevated from the highway, living on a high point in the area. not a gradual lump but more like on top of a finger poking out of the land with a significant slope towards the flat land and highway.

also does a river effect things/ in a sense that is usable geological data possible, the interstate has traffic all the time pretty much.

what would be a reasonable low cost primer test to see the type of hardware that can be used in the area, i will naturally tend to blow alot of money on precise equipment and over design noise floors and resolutions, so it would be good to have some kind of proofing test to discourage this kind of stuff if its going to end up being swamped with transit noise in the end.
« Last Edit: January 05, 2019, 02:10:22 pm by coppercone2 »
 

Offline EEVblog

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Re: Seismic Sensors
« Reply #6 on: January 05, 2019, 02:24:42 pm »
Sorry, don't know, I wasn't in the geology side of things, all I know is that our tank measurements got affected pretty easily.
 

Offline coppercone2

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Re: Seismic Sensors
« Reply #7 on: January 05, 2019, 03:29:38 pm »
as far as sensitivity i understand urban areas have a problem, i spoke to a professor that told me despite a floating granite table on air his laser measurements were obstructed by trucks passing across the street, however it was a much more urban area.

guess a ninety dollar gamble is not so bad
 

Offline coppercone2

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Re: Seismic Sensors
« Reply #8 on: January 05, 2019, 03:41:52 pm »
what would be a good starter circuit for a geophone that works well with the one you linked/

maybe a eevblog video/ ;D

 

Offline mark03

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Re: Seismic Sensors
« Reply #9 on: January 06, 2019, 03:14:41 am »
Instrumentation for local events (frequencies > 1 Hz) is easier but IMO less interesting than the teleseismic band below 1 Hz.  With even a rudimentary long-period seismometer you can see magnitude 6+ events in the same hemisphere and magnitude 7+ events worldwide, learn how the different wave components propagate, how we know that the Earth has a liquid core, etc.  As a bonus that frequency range is less susceptible to local noise sources.  The stuff you have to watch out for is not so much cars and footsteps as things like wind, or sunlight hitting the concrete slab you've placed the seismometer on.

For a geophone-based solution (mainly high frequency but maybe some teleseismic capability too), I recommend checking out the Raspberry Shake product.

The classic amateur long-period design, of amazing simplicity, is Lehman's "garden gate" seismometer from the Amateur Scientist column in Scientific American, July 1979.  Speaking from experience, this is an excellent gateway drug 8)   For a really serious, vertical broadband design with force feedback, google "FBV seismometer"; sadly there has never been a proper web site designed for this but several of the builders have nice pages describing theirs, e.g. http://www.groundmotion.org/main.html.  The "Yuma" is the most recent design for home builders and competes favorably with professional instruments costing tens of thousands of $$.  It has a flat response from 20 mHz to 30 Hz.  From a location in Seattle, mine sees most M5+ anywhere on the Pacific rim of fire, usually several events every day.  At this level the limiting factor is not the instrument but the site.  It helps if you are in the middle of a big continent to reduce microseism noise from the oceans, as does placing the instrument in a temperature-stabilized vault cut into bedrock.  OTOH mine sits on a concrete basement floor atop hundreds of feet of glacial till, and I'm happy with the results.
« Last Edit: January 06, 2019, 03:21:40 am by mark03 »
 
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Offline cdev

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Re: Seismic Sensors
« Reply #10 on: January 06, 2019, 03:22:31 am »
I've wanted to do this for years.. Tell me, how do you know the thickness of your glacial till, were you able to figure that out from your seismographs?  I also live on glacial till (between two long basalt outcroppings).

...Amateur Scientist column in Scientific American, July 1979.  Speaking from experience, this is an excellent gateway drug 8)   For a really serious, vertical broadband design with force feedback, google "FBV seismometer"; sadly there has never been a proper web site designed for this but several of the builders have nice pages describing theirs, e.g. http://www.groundmotion.org/main.html.  The "Yuma" is the most recent design for home builders and competes favorably with professional instruments costing tens of thousands of $$.  It has a flat response from 20 mHz to 30 Hz.  From a location in Seattle, mine sees most M5+ anywhere on the Pacific rim of fire, usually several events every day.  At this level the limiting factor is not the instrument but the site.  It helps if you are in the middle of a big continent to reduce microseism noise from the oceans, as does placing the instrument in a temperature-stabilized vault cut into bedrock.  OTOH mine sits on a concrete basement floor atop hundreds of feet of glacial till, and I'm happy with the results.
"What the large print giveth, the small print taketh away."
 

Offline mark03

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Re: Seismic Sensors
« Reply #11 on: January 06, 2019, 03:38:45 am »
I've wanted to do this for years.. Tell me, how do you know the thickness of your glacial till, were you able to figure that out from your seismographs?  I also live on glacial till (between two long basalt outcroppings).

I don't actually have a measurement---that [very round] number comes from a geological map and conversations with local geologists.  Be careful BTW, you might inadvertently give away your top-secret location  :-DD

If you can blast a pit or a vault out of the basalt, that would be a great place for a seismometer.  But the best "easy" place is usually your basement, if you have one.  You want to avoid big temperature swings.
 

Offline texaspyro

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Re: Seismic Sensors
« Reply #12 on: January 06, 2019, 04:20:55 am »
My seismic sensor is a "JM jug".  It is basically a magnet suspended on springs in a large coil of wire (with a neon light bulb across the coil to prevent handling damage from voltage spikes).  One problem with these is the coil can pick up interference from AM radio stations...

I also have a Worden gravity meter...
 
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Offline coppercone2

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Re: Seismic Sensors
« Reply #13 on: January 06, 2019, 09:53:46 am »
probobly a bad idea, but can you put it in a home well
 

Offline max_torque

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Re: Seismic Sensors
« Reply #14 on: January 06, 2019, 01:50:05 pm »


I used to work at the largest seismic water tank in the southern hemisphere

I've googled "seismic water tank" and all i get is lots of links to how to design water storage tanks that are earthquake proof!  I assume the test tank you are talking about Dave is to provide isolation for precision measurements?  Be interesting to hear more!
 

Offline babysitter

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Re: Seismic Sensors
« Reply #15 on: January 06, 2019, 03:19:12 pm »
Subscribe thread.

Just got some people at (A)Schaffenburg Makerspace interested in citizen science, have ordered 3 geophones from ebay, played with 1-20 Hz Sound reception, fired off a email to a nearby visitors mine for seismic setup.

I'm not a feature, I'm a bug! ARC DG3HDA
 

Offline rhb

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Re: Seismic Sensors
« Reply #16 on: January 06, 2019, 05:46:24 pm »
I spent my career in reflection seismology as a research scientist and programmer in the oil industry.  You will want to get the CWP/SU package.  You *might* want SLT/SU also, but it's unlikely to be of much help for your use case.  I supported CWP/SU for over 10 years and SLT/SU for 6.  I also arranged for SLT/SU to be transferred to Mines.

There is a wonderful wiki archived on the wayback machine of seismicunix.com with lots of usage examples.

Stockwell has retired and moved SU from the CWP site to github.

https://github.com/JohnWStockwellJr/SeisUnix/wiki

R. T. Clark has been the main equipment broker in the US for 30+ years..  I bought a 3 axis geophone from them 8-10 years ago for around $135.  I don't happen to see it on their website at the moment, but not much to them.  Plastic box w/ 3 spikes and 3 geophones inside.

Exploration seismology is very nearly on its death bed., so used land survey gear should be very cheap.

https://rtclark.com

*Everything* effects the response.  Topography is particularly difficult to deal with as it produces strange raypaths.

The most important question is what do you want to do?  Hobby science is easy.  Using multiple sensors to detect someone walking in the yard is a whole different ball game.

Exlporation geophones have poor low frequency response.  So if you're interested in earthquakes they are not suitable.

If you live somewhere reasonably quiet building a LaCoste-Romberg vertical and a pair of orthogonal horizontal axis seismographs would make an interesting project. Most of the cost would be in mounting the units solidly.

Using ambient noise as the source is called "seismic interferometery".  I never understood that naming.  But it stuck.
 
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Offline vindoline

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Re: Seismic Sensors
« Reply #17 on: January 06, 2019, 08:00:05 pm »
I don't know if it's the same thing, but Charles Wenzel has been experimenting with infrasound recently. He has lots of info, including diy microphones at his site: http://www.techlib.com/area_50/infrasound.htm
 
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Offline cdev

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Re: Seismic Sensors
« Reply #18 on: January 06, 2019, 08:31:47 pm »
This is also an amazingly cool program thats super useful in the time/frequency domain as a fine grained spectrum analysis tool.

https://www.qsl.net/dl4yhf/spectra1.html
"What the large print giveth, the small print taketh away."
 
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Offline radioactiveTopic starter

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Re: Seismic Sensors
« Reply #19 on: January 07, 2019, 08:28:16 am »
The classic amateur long-period design, of amazing simplicity, is Lehman's "garden gate" seismometer from the Amateur Scientist column in Scientific American, July 1979.  Speaking from experience, this is an excellent gateway drug 8)   For a really serious, vertical broadband design with force feedback, google "FBV seismometer"; sadly there has never been a proper web site designed for this but several of the builders have nice pages describing theirs, e.g. http://www.groundmotion.org/main.html.  The "Yuma" is the most recent design for home builders and competes favorably with professional instruments costing tens of thousands of $$. 

The Yuma FBV design and related looks really amazing.  Thank you for the information and links.  That helps a lot.
 

Offline radioactiveTopic starter

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Re: Seismic Sensors
« Reply #20 on: January 08, 2019, 04:43:46 am »
Interesting document comparing various sensor types.

Review of sensors for low frequency seismic vibration measurement
https://cds.cern.ch/record/1322403/files/CERN-ATS-Note-2011-001-TECH.pdf

After reading about the FBA type sensors, I'm wondering if this video from AppliedScience might be relevant.  Any thoughts on if it would be possible to use this approach for a vertical arrangement?  Please watch all the way to the end where it is demonstrated that you can pull the wavelength a few nm either way from center via supply modulation.
« Last Edit: January 09, 2019, 07:01:17 am by radioactive »
 

Offline GK

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Re: Seismic Sensors
« Reply #21 on: January 11, 2019, 02:18:49 am »
Spent ~13 of my 15 years in government assisting in upgrading and maintaining the (since disbanded) seismic monitoring network for the whole state of South Australia and have been on more field trips to deploy temporary equipment for aftershock surveys than I can remember.

I've never seen a geophone used to monitor natural seismicity. I've only had anything to do with geophones for induced seismicity, such as when letting off charges or for teaching purposes banging a metal plate on the ground with a sledgehammer. I have some geophones which I've collected and have thought about sticking them in the ground, but they are just too insensitive and really don't have the low frequency response required to make a decent seismometer.

We always operated on a shoestring budget and the state seismologist kept quite a large amount of antique/legacy equipment in active use just to keep the monitoring network as large as practically possible. We had a lot of Ranger SS-1 short-period seismometers in use - originally developed for the moon (the lunar Ranger Missions) and only recently (a few years ago) finally discontinued by Kinemetrics. From a hobby perspective with a limited budget, a used SS-1 from ebay or some specialist test/scientific equipment reseller would be a excellent start. They are mechanically simple and easily repaired. An SS-1 suitably installed will pick up those 7 and 8s overseas no problem.

The best seismometers for distant earthquakes though are the long-period units with huge/heavy sprung masses. The farther away the epicenter of the earthquake, the lower the frequency of the shock waves. Think of a stone dropped into a body of water - as the ripples radius outwards they dissipate as the wavelengths grow longer and longer. We had some long-period Benioff seismometers dating back to the 50s/60s that weighed, IIRC, a couple of hundred kg each. They had no high-frequency response to speak of so the noise was really low. These were installed in concrete bunkers on huge concrete plinths. Probably not practical for the average hobbyist, but in response to a big enough overseas wobble (our in-house technical term for earthquakes in general) they could continue to respond for an hour or more.

A couple of our modern sensors for picking up local seismicity, that I recall, were the 3ESP and the CMG-5T from Guralp:

http://www.essearth.com/product/weak-motion-seismometer/
http://www.essearth.com/product/strong-motion-feedback-accelerometer/




« Last Edit: January 11, 2019, 04:28:38 am by GK »
Bzzzzt. No longer care, over this forum shit.........ZZzzzzzzzzzzzzzzz
 
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Offline EEVblog

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Re: Seismic Sensors
« Reply #22 on: January 11, 2019, 02:38:56 am »
I used to work at the largest seismic water tank in the southern hemisphere

I've googled "seismic water tank" and all i get is lots of links to how to design water storage tanks that are earthquake proof!  I assume the test tank you are talking about Dave is to provide isolation for precision measurements?  Be interesting to hear more!

Yes, above ground test tanks vibration isolated on huge rubber mounts and other mechanisms. IIRC the one on the Thomson Marconi Sonar site was maybe 6-8m in diameter and 20m deep. I think the Marconi one was a bit smaller, but also above ground.
I've tried but can't find any photos of them, this was in the days before digital cameras and the photo happy craze we have these days.
Maybe I should try and ask if it's still there and get a tour?
 
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Offline radioactiveTopic starter

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Re: Seismic Sensors
« Reply #23 on: January 11, 2019, 02:52:32 am »
Quote
Maybe I should try and ask if it's still there and get a tour?
  I would like to watch that!
 

Offline diegogmx

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Re: Seismic Sensors
« Reply #24 on: January 11, 2019, 06:37:31 am »
One interesting method i know modern seismometers use is to have a test mass as an lvdt moving element, and using a control loop and a coil to keep the lvdt output at 0, the seismometer output waveform would be the output of the control loop, they use one of these for each axis, buying one of these would most likely be prohibitively expensive yet it would be an interesting (and probably damn hard) project for summer (unless you are in the north hemisphere) :)
 
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