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Threshold magnitudes for a multichannel correlation detector in background seismicity

Joshua D. Carmichael and Hans Hartse
Threshold magnitudes for a multichannel correlation detector in background seismicity
Bulletin of the Seismological Society of America (April 2016) 106 (2): 478-498

Abstract

Colocated explosive sources often produce correlated seismic waveforms. Multichannel correlation detectors identify these signals by scanning template waveforms recorded from known reference events against target data to find similar waveforms. This screening problem is challenged at thresholds required to monitor smaller explosions, often because nontarget signals falsely trigger such detectors. Therefore, it is generally unclear what thresholds will reliably identify a target explosion while screening nontarget background seismicity. Here, we estimate threshold magnitudes for hypothetical explosions located at the North Korean nuclear test site over 6 months of 2010, by processing International Monitoring System (IMS) array data with a multichannel waveform correlation detector. Our method (1) accounts for low-amplitude background seismicity that falsely triggers correlation detectors but is unidentifiable with conventional power beams, (2) adapts to diurnally variable noise levels, and (3) uses source-receiver reciprocity concepts to estimate thresholds for explosions spatially separated from the template source. We find that underground explosions with body-wave magnitudes m (sub b) approximately 1.66 are detectable at the IMS array USRK with probability 0.99, when using template waveforms consisting only of Pwaves, without false alarms. We conservatively find that these thresholds also increase by up to a magnitude unit for sources located 4 km or more from the 12 February 2013 announced nuclear test.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 106
Serial Issue: 2
Title: Threshold magnitudes for a multichannel correlation detector in background seismicity
Affiliation: Los Alamos National Laboratory, Los Alamos, NM, United States
Pages: 478-498
Published: 201604
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 50
Accession Number: 2016-054074
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. sketch map
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201626
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