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Detection of long-period S from earthquakes and explosions at LASA and LRSM stations with application to positive and negative discrimination of earthquakes and underground explosions. Technical report

Technical Report ·
OSTI ID:7365283
An improved distance-amplitude relation for long-period S waves is developed and applied to long-period S waves measured from megaton-range explosions. The difference between magnitude determined from the maximum amplitude long-period S waves and the magnitude determined from Rayleigh waves is found to be a good discriminant between worldwide earthquakes and explosions at NTS and Amchitka. The long-period SH/SV ratio is not a discriminant. The 90% incremental threshold for detection of earthquake long-period S waves at LASA from Japan and the Kuril Islands is m/sub b/ = 5.2. Beamforming and program FKCOMB were found to be equal in detection capability. Previously reported data imply a 90% incremental threshold of m/sub b/ = 4.7 for detection of long-period S waves at ALPA from the Kuril Islands and Kamchatka. The difference between LASA and ALPA capability can be explained by the average distance-amplitude relation together with the lower noise level at ALPA. For possible seismic network, the use of negative discriminants (no detection of S waves) with .01 probability of a false alarm for explosions is shown to result in an M/sub s/ threshold approximately equal to the threshold of 90% probability of detection of S waves from earthquakes by two or more stations (positive discrimination). A significant lowering of the negative threshold is possible if one station of the network has an especially low detection threshold.
Research Organization:
Teledyne Geotech, Alexandria, Va. (USA). Seismic Data Lab.
OSTI ID:
7365283
Report Number(s):
AD-A-013672/1ST; SDAC-TR-74-15
Country of Publication:
United States
Language:
English