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Seismic Sensors

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cdev:
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).


--- Quote from: mark03 on January 06, 2019, 03:14:41 am ---...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.

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mark03:

--- Quote from: cdev 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).

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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.

texaspyro:
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...

coppercone2:
probobly a bad idea, but can you put it in a home well

max_torque:

--- Quote from: EEVblog on January 05, 2019, 01:10:15 pm ---

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

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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!

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