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Focal depth determination for moderate and small earthquakes by modeling regional depth phases sPg, sPmpP and sPn

Shutian Ma
Focal depth determination for moderate and small earthquakes by modeling regional depth phases sPg, sPmpP and sPn
Bulletin of the Seismological Society of America (June 2010) 100 (3): 1073-1088

Abstract

There are three usable regional depth phases, sPg, sPmP, and sPn, and their corresponding reference phases, Pg, PmP, and Pn. The differential time between each depth phase and its reference phase can be used to estimate earthquake focal depth. We have developed a method to determine focal depth for moderate and small earthquakes by using a regional depth-phase modeling (RDPM) method. We used a default focal mechanism to generate the differential times for all earthquakes. To estimate the reliability of the modeled focal depths, we compared our solutions with those obtained by other methods and found the consistency is good. Because the focal depths estimated by RDPM are model dependent, we tested the extent of the dependency and found that a 10% error in the crustal model may generate a 10%-15% error in the modeled depth. The absolute error is determined by the error in the crustal model and the focal depth itself. We found that earthquake location errors have only a small effect on the modeled focal depths. By analyzing synthetic and observed waveforms, we found a distance window within which sPmP and PmP are well developed, and, within the window, the P portion of the waveform is relatively simple and sPmP and PmP are easy to identify. We also demonstrated that the assumptions of sPmP and PmP are correct, that regional depth phases are not developed or not discernible in some regions, and that regional depth phases have special features that can be used to identify those phases.


ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 100
Serial Issue: 3
Title: Focal depth determination for moderate and small earthquakes by modeling regional depth phases sPg, sPmpP and sPn
Author(s): Ma, Shutian
Affiliation: University of Western Ontario, Department of Earth Sciences, London, ON, Canada
Pages: 1073-1088
Published: 201006
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 30
Accession Number: 2010-059074
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N42°00'00" - N84°00'00", W141°00'00" - W52°00'00"
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: 201032
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