Post-1906 stress recovery of the San Andreas fault system calculated from three-dimensional finite element analysis

Journal of Geophysical Research B: Solid Earth
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Abstract

The M = 7.8 1906 San Francisco earthquake cast a stress shadow across the San Andreas fault system, inhibiting other large earthquakes for at least 75 years. The duration of the stress shadow is a key question in San Francisco Bay area seismic hazard assessment. This study presents a three-dimensional (3-D) finite element simulation of post-1906 stress recovery. The model reproduces observed geologic slip rates on major strike-slip faults and produces surface velocity vectors comparable to geodetic measurements. Fault stressing rates calculated with the finite element model are evaluated against numbers calculated using deep dislocation slip. In the finite element model, tectonic stressing is distributed throughout the crust and upper mantle, whereas tectonic stressing calculated with dislocations is focused mostly on faults. In addition, the finite element model incorporates postseismic effects such as deep afterslip and viscoelastic relaxation in the upper mantle. More distributed stressing and postseismic effects in the finite element model lead to lower calculated tectonic stressing rates and longer stress shadow durations (17–74 years compared with 7–54 years). All models considered indicate that the 1906 stress shadow was completely erased by tectonic loading no later than 1980. However, the stress shadow still affects present-day earthquake probability. Use of stressing rate parameters calculated with the finite element model yields a 7–12% reduction in 30-year probability caused by the 1906 stress shadow as compared with calculations not incorporating interactions. The aggregate interaction-based probability on selected segments (not including the ruptured San Andreas fault) is 53–70% versus the noninteraction range of 65–77%.

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Publication type Article
Publication Subtype Journal Article
Title Post-1906 stress recovery of the San Andreas fault system calculated from three-dimensional finite element analysis
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1029/2001JB001051
Volume 107
Issue 8
Year Published 2002
Language English
Publisher American Geophysical Union
Description 13 p.
First page ESE 3-1
Last page ESE 3-13
Country United States
State California
Other Geospatial San Andreas Fault
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