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A bilinear source-scaling model for M-log a observations of continental earthquakes

Bulletin of the Seismological Society of America

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DOI: 10.1785/0120010148

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Abstract

The Wells and Coppersmith (1994) M-log A data set for continental earthquakes (where M is moment magnitude and A is fault area) and the regression lines derived from it are widely used in seismic hazard analysis for estimating M, given A. Their relations are well determined, whether for the full data set of all mechanism types or for the subset of strike-slip earthquakes. Because the coefficient of the log A term is essentially 1 in both their relations, they are equivalent to constant stress-drop scaling, at least for M ??? 7, where most of the data lie. For M > 7, however, both relations increasingly underestimate the observations with increasing M. This feature, at least for strike-slip earthquakes, is strongly suggestive of L-model scaling at large M. Using constant stress-drop scaling (???? = 26.7 bars) for M ??? 6.63 and L-model scaling (average fault slip u?? = ??L, where L is fault length and ?? = 2.19 × 10-5) at larger M, we obtain the relations M = log A + 3.98 ?? 0.03, A ??? 537 km2 and M = 4/3 log A + 3.07 ?? 0.04, A > 537 km2. These prediction equations of our bilinear model fit the Wells and Coppersmith (1994) data set well in their respective ranges of validity, the transition magnitude corresponding to A = 537 km2 being M = 6.71.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A bilinear source-scaling model for M-log a observations of continental earthquakes
Series title:
Bulletin of the Seismological Society of America
DOI:
10.1785/0120010148
Volume
92
Issue:
5
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1841
Last page:
1846
Number of Pages:
6