Thanks, My old and hated statistics class is coming back to me. I agree that I could filter or band pass most of the noise. My interest in combining the seismometer outputs arose mainly because I have the 3 seismometers and I wanted to get the most from them (I'm the guy who hoped that you could convert a vertical to horizontal). If it is possible to combine the outputs after signal processing, why would it not be possible to do it with the raw signals, i.e. directly out of the units. Wouldn't you be looking as a sum of the voltages? Dick __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>