A maximum rupture model for the southern San Andreas and San Jacinto Faults California, derived from paleoseismic earthquake ages: What limits does it provide for MFDs?

Kate Scharer


Date & Time
Online-only seminar via Microsoft Teams
Elizabeth Cochran

Paleoseismic rupture histories provide spatio-temporal models of earthquake moment release that lengthen the instrumental catalogue and can be used to evaluate numeric rupture models and forecasts. I review a rupture model designed to produce the fewest and thus largest magnitude earthquakes using paleoseismic dates from the southern San Andreas and San Jacinto fault (Scharer and Yule, 2020). I highlight new paleoseismic data from the San Gorgonio Pass region that restrict ruptures along the “ShakeOut” rupture path and suggests these ruptures alternate with periods of activity in the Cajon Pass region. Overall, the rupture history supports inferences from dynamic and quasi-static rupture modeling. Based solely on the ages of paleoearthquakes, the maximum rupture model produces rupture frequencies and a magnitude distribution similar to the historic record and a comparison of independent data of slip per earthquake with the average slip along the faults derived from the rupture model shows that missed events are unlikely. Thus, although it is an end-member model, it should provide a reasonable comparison for magnitude-frequency distributions derived from earthquake rupture forecasts. Sub-regional clustering suggested by the model deserves additional study into the underlying physical properties that would promote such behavior in southern California and the timescales over which it could occur.

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