Thomas, Darrell, Danie, Re: "Goodbye cruel ..."; of course we all know that seismographs attract earthquakes like lightning rods, so your chance of your wallet being swallowed by a fissure increases exponentially with your success at amateur seismology. (I have actually encountered this quake attraction thinking in trying to permit telemetry station sites in the Ozarks.) Regarding the Wood-Anderson torsional seismometer: I have operated several versions of this, including the original wooden box designs and the later compact refinements by Q.E.D. Early instruments were set to modest periods, with 2.7 seconds being common, but relatively unstable. Later a standard of 0.8 seconds and a magnification of 2800 was agreed on for a standard 60mm/min photographic record. Because its magnification is so low, real data was a rarity unless you were close to an active fault zone. But for larger quakes it was very useful for calculating the Richter magnitude, which was based on the instrument. Since they were horizontal sensors, we photo-recorded them on a triple- record drum along with a high gain 1 second vertical seismometer/galvanometer system. But photo-recording became costly and was complicated and relatively time consuming, so currently the W-As are adornments in a display case, and the W-A response can be derived from any broadband signal and scaled to any near-field magnitude. The original article by Anderson and Wood was published in the BSSA, vol 15, pp 1072, in 1925. Regards, Sean-Thomas __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>