Southern San Andreas Fault seismicity is consistent with the Gutenberg-Richter magnitude-frequency distribution

Bulletin of the Seismological Society of America
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Abstract

The magnitudes of any collection of earthquakes nucleating in a region are generally observed to follow the Gutenberg-Richter (G-R) distribution. On some major faults, however, paleoseismic rates are higher than a G-R extrapolation from the modern rate of small earthquakes would predict. This, along with other observations, led to formulation of the characteristic earthquake hypothesis, which holds that the rate of small to moderate earthquakes is permanently low on large faults relative to the large-earthquake rate (Wesnousky et al., 1983; Schwartz and Coppersmith, 1984). We examine the rate difference between recent small to moderate earthquakes on the southern San Andreas fault (SSAF) and the paleoseismic record, hypothesizing that the discrepancy can be explained as a rate change in time rather than a deviation from G-R statistics. We find that with reasonable assumptions, the rate changes necessary to bring the small and large earthquake rates into alignment agree with the size of rate changes seen in epidemic-type aftershock sequence (ETAS) modeling, where aftershock triggering of large earthquakes drives strong fluctuations in the seismicity rates for earthquakes of all magnitudes. The necessary rate changes are also comparable to rate changes observed for other faults worldwide. These results are consistent with paleoseismic observations of temporally clustered bursts of large earthquakes on the SSAF and the absence of M greater than or equal to 7 earthquakes on the SSAF since 1857.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Southern San Andreas Fault seismicity is consistent with the Gutenberg-Richter magnitude-frequency distribution
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120140340
Volume 105
Issue 4
Year Published 2015
Language English
Publisher Seismological Society of Amercia
Contributing office(s) Earthquake Science Center
Description 11 p.
First page 2070
Last page 2080
Country United States
State California
Other Geospatial Southern San Andreas Fault
Online Only (Y/N) N
Additional Online Files (Y/N) N