LARGE APERTURE SEISMIC ARRAYS (LASA)
Quarterly technical rept. no. 1
GENERAL ATRONICS CORP PHILADELPHIA PA
Pagination or Media Count:
Four topics are discussed in the report. The first topic related to the high-frequency 4-5 Hz portion of LASA seismograms. Data are cited which indicate a statistically significant amount of signal energy in this region, and preliminary unsuccessful efforts at combining high-pass filtered records from nearby seismometers are described. The second topic is the problem of detecting underground nuclear tests in the presence of large natural events. A hypothetical detection system consisting of a number of single seismometers at close range and a continental-size array at teleseismic range is analyzed and discussed. The third topic is DIMUS processing of seismic array out-puts. The conventional DIMUS processing consists of hardlimiting each seismogram thereby yielding a one bit per sample representation and then proceeding as with the unaltered seismograms. Two modified DIMUS schemes, which require a single analog channel, are considered. The performance of these schemes, conventional DIMUS, and conventional analog arrays is evaluated for the spectral-ratio and complexity diagnostics. Finally, an extended version of an automatic pP test is discussed. Initial calculations are presented that suggest that this test will yield satisfactory depth picks for earthquakes as deep as 150 km.
- Seismic Detection and Detectors