L{sub g} coda moment rate spectra and discrimination using L{sub g} coda envelopes

Conference · Fri Dec 30 23:00:00 EST 1994

OSTI ID:96003

Mayeda, K M; Walter, W R ^[1]

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1. Lawrence Livermore National Laboratory, CA (United States)

Low magnitude seismic monitoring will depend largely on high frequency near-regional discriminants such as ratios of P to S energy and spectral amplitude ratios within P or S phases. Due to high frequency attenuation and sparse distribution of recording stations, small magnitude events will have to be identified with only a few stations, in some instances perhaps only one. Recently, stable single station magnitudes for explosions at NTS and moment rate spectra for earthquakes throughout the western U.S. have been estimated using L{sub g} coda envelopes. The averaging nature of coda waves virtually eliminates the amplitude variability due to source radiation anisotropy and lateral variations in path geology between the source and receiver. In this study, we find that L{sub g} coda spectral ratios are 3 to 4 times less variable than direct phase spectral ratio measurements. Events fired in low strength-high gas porosity material have higher spectral ratios than events in high strength-low gas porosity material, and thus discriminate well from earthquakes which have the lowest spectral ratios. In contrast, P{sub g}/L{sub g} phase ratios for events in low strength-high gas porosity material lie closest to the earthquake population. A combination of both discriminants performs better than either one does alone. Moment rate spectra for explosions show strong depth-dependent spectral peaking that is not observed in normal depth western U.S. earthquakes and is consistent with strong R{sub g} to S scattering near the explosion source. This explosion spectral peaking will be explored in future work as part of a possible broadband discriminant.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• OSTI ID: 96003
• Report Number(s): CONF-9404100--; ON: DE95011413
• Country of Publication: United States
• Language: English

Related Subjects

35 ARMS CONTROL
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
AMMONIUM NITRATES
AMPLITUDES
CHEMICAL EXPLOSIONS
COMPARATIVE EVALUATIONS
DETONATIONS
EARTHQUAKES
FUEL OILS
GROUND MOTION
NEVADA TEST SITE
NON-PROLIFERATION TREATY
NUCLEAR EXPLOSION DETECTION
NUCLEAR EXPLOSIONS
SEISMIC DETECTION
SEISMIC DETECTORS
SEISMOGRAPHS
SPECTRA
UNDERGROUND EXPLOSIONS
VERIFICATION
WAVE FORMS
WAVE PROPAGATION