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A spectrogram-based method of Rg detection for explosion monitoring

Colin T. O'Rourke and G. Eli Baker
A spectrogram-based method of Rg detection for explosion monitoring
Bulletin of the Seismological Society of America (December 2016) 107 (1): 34-42


The detection of the high-frequency fundamental-mode Rayleigh-wave Rg is important for explosion monitoring efforts because it indicates a shallow source, which is most often man-made. We developed an automated Rg detector that successfully identifies Rg using the spectrogram of the seismic signal to find peaks in the characteristic Rg frequency band. We tested the detector using a network of over 200 seismometers in Wyoming, which recorded dozens of nearby coal-mining blasts and active-source tamped borehole shots. The detector finds peaks in the summed spectrogram amplitudes from 0.4 to 0.8 Hz for mining blasts and from 0.8 to 1.5 Hz for borehole shots. We achieved successful Rg detection of mining blasts across the entire array for the largest blasts, though smaller blasts had less success at distant stations, due to low signal amplitude. Similarly, Rg detection from borehole shots was successful at distances <50 km but was not common at farther stations. We then developed a method to estimate the probability that a null detection was indicative of a deep source and not an explosion with low signal-to-noise ratio. Finally, we compared our method with an existing Rg detection method based on finding retrograde particle motion, typical of Rg, in signal coming from the known source-receiver back azimuth. In our application, the detector worked well for more distant stations but failed at stations within the same basin as the source, where Rg has prograde particle motion. The two detectors are fundamentally different; the new detector is easier to automate but depends on Rg having larger amplitude than the pre-Rg time window, whereas the existing detector triggers based on the particle motion and the direction of arrival, independent of the amplitude. The new method, perhaps in conjunction with the existing method, can offer increased monitoring capability and higher confidence when detecting Rg. Electronic Supplement:Tables of source information and figures of example detection.

ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 107
Serial Issue: 1
Title: A spectrogram-based method of Rg detection for explosion monitoring
Affiliation: Kirtland Air Force Base, Air Force Research Laboratory, Albuquerque, NM, United States
Pages: 34-42
Published: 20161206
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 20
Accession Number: 2017-006204
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N43°00'00" - N45°00'00", W110°00'00" - W105°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201705
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