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Seismic hazard estimate from background seismicity in Southern California

Tianqing Cao, Mark D. Petersen and Michael S. Reichle
Seismic hazard estimate from background seismicity in Southern California
Bulletin of the Seismological Society of America (October 1996) 86 (5): 1372-1381


We analyzed the historical seismicity in Southern California to develop a rational approach for calculating the seismic hazard from background seismicity of magnitude 6.5 or smaller. The basic assumption for the approach is that future earthquakes will be clustered spatially near locations of historical mainshocks of magnitudes equal to or greater than 4. We analyzed the declustered California seismicity catalog to compute the rate of earthquakes on a grid and then smoothed these rates to account for the spatial distribution of future earthquakes. To find a suitable spatial smoothing function, we studied the distance (r) correlation for Southern California earthquakes and found that they follow a 1/r (super mu ) power-law relation, where mu increases with magnitude. This result suggests that larger events are more clustered in space than smaller earthquakes. Assuming the seismicity follows the Gutenberg-Richter distribution, we calculated peak ground accelerations (PGA) for 10% probability of exceedance in 50 yr. PGA estimates range between 0.25 and 0.35 g across much of Southern California. These ground-motion levels are generally less than half the levels of hazard that are obtained using the entire seismic source model that also includes geologic and geodetic data. We also calculated the overall uncertainty for the hazard map using a Monte Carlo method and found that the coefficient of variation is about 0.24+ or -0.01 for much of the region.

ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 86
Serial Issue: 5
Title: Seismic hazard estimate from background seismicity in Southern California
Affiliation: California Department of Conservation, Division of Mines and Geology, Sacramento, CA, United States
Pages: 1372-1381
Published: 199610
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 26
Accession Number: 1997-008909
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 199703
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