Geophones for Recording EQ’s OVERVIEW Local Events Aftershock Deployments Extend Period for Regional Events Simple Checks to Assure Sensor Works

Seismometer Responses: Ammon-SLU

Ground Motion Amplitudes (displacement)

1999 PH’D Stanford U.

Neg FeedBack- Lippman method (1983) Lennartz (German company) 4.5 Hz to 1 Hz (1s), 0.2 Hz (5s); and 0.05 Hz (20s)

Volcan Array uses L15 If you want an affordable array start with an affordable sensor

Two Other Methods By inverse filtering electronically (analog) Roberts (Equivalent) Circuit Peter M. Roberts, October 1989, BSSA, Vol.79, No 4, pp By Digitally Applying Transfer Fn. Deconvolve- Easiest way

Geophone Specifications: How to read a spec. sheet for 4.5 Hz, 10 Hz, responses High pass filters with a 40 dB/decade roll off 2 pole filter Measure ground velocity- Output ~40V/m/s How to measure Resistance: Rc coil resistance Rs shunt resistance Rt total resistance

Check polarity: Tilt test Tap test How to increase output signal: Put them in series Huddle Test: Determines if they all work the same If not, are they coupled properly?