[GreenKeys] OT -- diy earthquake detector?

[Richard Knoppow]

    An old friend who kept horses said they knew when an 
earthquake was coming.  He was a scientist for JPL so not easily 
fooled.
     I have been in a couple of quite strong earthquakes, they 
are very frightening and I don't think one ever gets used to 
them. My next door neighbor had never felt one before but this 
was not a strong shaker here some hundred miles from its 
epicenter, no damage and nothing fell down (including me), 
nonetheless to say the least it impressed him. Even the weak ones 
get your attention.
On 7/8/2019 7:17 PM, Gil Smith wrote:
> Hey folks:
> 
> What with all the earthquake activity of late, I thought I would 
> dig out an old geophone from decades ago (when I was with a 
> company in Houston designing seismic gear for the oil industry).
> 
> A geophone is a moving-coil/magnet sensor for detecting velocity 
> of the earth -- not the best sensor for rolling earthquake waves, 
> as it is designed for detecting in just the vertical axis and is 
> only moderately sensitive, but fun to try nevertheless.
> 
> Since the geophone generates analog signals in the microvolt to 
> millivolt range, it is just dandy to connect to a low-noise, 
> low-freq adc system I happen to have lying around.
> 
> The geophone was placed on the concrete floor in my lab, and 
> connected to channel 1 on the adc system.  No signal conditioning 
> circuitry other than a damping resistor.  In the attached 
> screenshot you can see significant pulses on the yellow channel 1 
> trace -- this is me walking on the concrete floor with no shoes 
> on.  Perhaps there is a market in the security industry for 
> protecting bank vaults :)
> 
> Probably won't see any distant earthquake activity from Cali, but 
> I would bet it could detect local seismic events here in AZ (not 
> that we have many).
> 
> You might say why not a modern mems accelerometer, which would be 
> interesting to try also, but they are notoriously noisy, and it 
> would be a digital interface with custom code -- the geophone 
> connection took less than a minute of soldering to a connector.
> 
> But it got me looking around at diy seismometer sensors that are 
> a better fit.  I might try building one for fun.
> 
> gil
> 

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL