Barry- I was intrigued by your question so I used it as an excuse to get my WinQuake act together and install the most recent version, v 2.6. A M5.8 earthquake is going to have an S-wave corner frequency near 1 Hz, and it can also generate alot of Raleigh waves on the vertical that are peaked at even lower frequencies. The S-wave corner frequency is controlled by the fault dimension, and to first order, it is equal to the reciprocal of the S-wave travel time along the fault, i.e., the fault length divided by the S-wave velocity. I looked at the spectra of your record and noted that it was flat from about 10 Hz (where you must have your low-pass, anti-aliasing-filter corner frequency) down to 0.5 Hz where your high-pass is. It would be interesting to see the record before you high-passed it: it should start rolling off at lower frequencies somewhere just below 1 Hz. In the absence of instrument response, in theory, the acceleration spectrum should be flat in the band that extends from the S-wave corner-frequency up to f_max -- the high-frequency limit caused by the low-pass filter characteristics of the Earth. -Edward barry lotz wrote: > Hi > I've uploaded a new event file for a small vertical "strong motion" > accelerometer. I'm not to familiar with acceleration recording accept > that I realize the frequency content is a higher. I increased my sample > rate for the Lehman and this sensor to 50 hz. I was surprised to get > little long period content in this recording. Is this common for > accelerations? -- Edward Cranswick Tel: 303-273-8609 US Geological Survey, MS 966 Fax: 303-273-8600 PO Box 25046, Federal Center cranswick@........ Denver, CO 80225-0046 USA E.M. Forster said, "Only connect". __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>