Accession Number : ADA320873

Title :   Transportable Time Domain Discriminants.

Descriptive Note : Final rept. 15 Jun 95-14 Jun 96,

Corporate Author : CALIFORNIA INST OF TECH PASADENA

Personal Author(s) : Hemberger, Donald V. ; Zhu, Lupei ; Burdick, Larry

PDF Url : ADA320873

Report Date : 23 AUG 1996

Pagination or Media Count : 49

Abstract : We have examined broadband waveforms from a large number of NTS explosions and earthquakes throughout the southwestern United States in order to characterize seismic sources. Explosions were found to be richer in coda energy than earthquakes. Most earthquakes show relatively little long-period (T>4 sec) coda energy and tend to be richer in long-period and shear-wave energy than explosions. We have developed several seismic discriminants based on these observations and our modeling experience. One promising discriminant is the ratio of short-period vertical components, P-wavetrain energy, to long-period surface wave energy, averaged over three components. Explosions tend to have a higher ratio than do earthquakes, essentially an extension of Mb:M5. Magnitude threshold for this discriminant is about 3.5. Another useful discriminant is based on the total broadband energy to moment ratio where explosions are distinguished by their stronger energy levels relative to their long-period amplitudes. This approach requires Green's functions, a source estimator program, and processes all events as earthquakes. For this method to be effective requires the calibration of the region using relatively large earthquakes, M>5, but does not require calibrations of explosions.

Descriptors :   *NUCLEAR EXPLOSIONS, *SEISMIC DISCRIMINATION, *EARTHQUAKES, SEISMIC DATA, CALIFORNIA, GREENS FUNCTIONS, TIME DOMAIN, PULSE AMPLITUDE, PRIMARY WAVES(SEISMIC WAVES), SEISMIC ARRAYS, SECONDARY WAVES, SEISMOGRAPHS, SURFACE ENERGY, PHASE VELOCITY.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE