Date Mon, 21 Oct 2002 152035 EDT

Hi John,

Since last Monday, I have been recording part time, looking for events to prove whether it works well or not. The week has been pretty quiet, but I managed to pick two events on October 19. One was magnitude 5.9 in Irian Jaya, and the second in the Kuril Islands, magnitude 6.2. I made up a GIF image comparing my digitally processed long-period plots using my DrumPlot program to those of nearby station PAL, which is attached.

q0210191.gif (28252 bytes)

The sensor operates at 11-second period, with 0.62 damping. The only drawback to digitally extending the period to 32 seconds or more is that the record contains transients from people moving about upstairs near the basement location of the sensor. The basement floor deflects slightly, causing a tilt response in the sensor. Of course, a sensor operating at 32-second period at the same basement floor location would have the same problem.


Bob McClure