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Understanding the differences between three teleseismic m (sub b) scales

John P. Granville, Paul G. Richards, Won-Young Kim and Lynn R. Sykes
Understanding the differences between three teleseismic m (sub b) scales
Bulletin of the Seismological Society of America (October 2005) 95 (5): 1809-1824


We investigate differences between three body-wave magnitude (m (sub b) ) scales for 2009 earthquakes from 1996 to 1999 listed in the Preliminary Determination of Epicenter (PDE) bulletin having m (sub b) between 5.0 and 5.5 and that also have moment tensor solutions available from the Harvard Centroid Moment Tensor (CMT) catalog. A total of 31,280 broadband seismograms are analyzed, for an average of 15 stations per event. Both the PDE and Reviewed Event Bulletin (REB) procedures for determining an automated m (sub b) are reproduced, thereby eliminating any discrepancies that result from using different networks of stations. We compare the reproduced PDE and REB magnitudes to another magnitude measurement, m (sub b) (P), that is based on the Worldwide Standard Seismographic Network (WWSSN) short-period instrument. We find that differences between m (sub b) (P), m (sub b) (PDE), and m (sub b) (REB) arise from four factors: response function, length of time window, and corrections for event depth and epicentral distance. Reproduced m (sub b) (PDE) and m (sub b) (P) are strongly correlated, and we expect that magnitudes assigned from WWSSN short-period instruments during the 1970s and 1980s are consistent with those assigned by the automated procedure used since 1991 by the U.S. Geological Survey (USGS), providing stability in m (sub b) measurements over several decades. The difference between m (sub b) (REB) and m (sub b) (P) is much greater because of the significantly shorter REB window length of 5.5 sec and the high-frequency passband of the REB displacement response.

ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 95
Serial Issue: 5
Title: Understanding the differences between three teleseismic m (sub b) scales
Affiliation: Lamont-Doherty Earth Observatory, Palisades, NY, United States
Pages: 1809-1824
Published: 200510
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 18
Accession Number: 2005-076341
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N20°00'00" - N53°00'00", E74°00'00" - E135°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: 200545
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