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Investigating the effectiveness of P/S amplitude ratios for local distance event discrimination

Moira L. Pyle and William R. Walter
Investigating the effectiveness of P/S amplitude ratios for local distance event discrimination
Bulletin of the Seismological Society of America (June 2019) 109 (3): 1071-1081

Abstract

The ability to discriminate between underground explosions and earthquakes is an important operation for global security and test-ban-treaty monitoring, and seismology plays a key role in this endeavor. The use of seismic P- to S-wave amplitude ratios has been demonstrated to be an effective discriminant at regional distances for a variety of emplacement conditions and test sites around the world. Increasing interest in detecting and discriminating smaller events, both for purposes of nuclear monitoring and seismic hazard estimation, requires the use of data with shorter event-to-station paths. At these local distances (< or =200 km), the use of P/S ratios for event discrimination is poorly studied compared with regional distances (200-1500 km). The path averaging that allows for relatively simple corrections to P/S ratios to remove bias from along-path structural differences at regional distances may be insufficient to remove enough scatter from the ratios to allow for accurate event identification at local distances. We use data from a series of chemical explosions detonated as part of the Source Physics Experiment at the Nevada National Security Site in southern Nevada and surrounding seismicity to investigate the discrimination performance of P/S ratios at local distances. We find that discrimination at individual stations is highly variable, regardless of frequency. Network averaging of ratios improves discrimination performance above 6 Hz, as a result of the reduction of scatter among the earthquake ratios. However, azimuthal and distance-limited averaging suggests that explosion ratios are affected by a complicated source and path relationship that may lead to substantial variability in local P/S ratios at different locations.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 109
Serial Issue: 3
Title: Investigating the effectiveness of P/S amplitude ratios for local distance event discrimination
Affiliation: Lawrence Livermore National Laboratory, Livermore, CA, United States
Pages: 1071-1081
Published: 201906
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 30
Accession Number: 2019-062019
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N35°00'00" - N39°00'00", W118°00'00" - W115°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201915
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