[time-nuts] Using oscillators to measure earthquakes

[Mark Sims]

Today the Dallas area has been experiencing several eathquakes.  The largest were magnitude 3.2, 3.6, and 3.1 at a depth of around 4km.    They happened around every three hours. I am around 5 miles from the epicenter.  They are strong enough to shake the house quite a bit.  The largest put a hairline crack in some sheetrock.
After the second one I cobbled up a sensor using an old "tight pll" type of circuit that I was playing with several years ago,  24 bit A/D,  and an AVR based touch-screen microcontroller.  I hacked up some quick code to monitor and graph the A/D.   Inputs to the circuit were an HP5065 and a rather woogedy 5 MHz OCXO.   The oscillator was placed on my garage floor and weighted down with a 2kg calibration weight.   Woo hoo!  the last quake did produce a measurable signal...  Now I have to figure out a way to get the data off the micro-controller...