Rupture Models and Ground Motion for Shakeout and Other Southern San and Reas Fault Scenarios

Abstract eng:
The SoSAFE (Southern San Andreas Fault Evaluation) ShakeOut scenario has been considered as potential strong earthquake (Mw 7.81±0.06) expected from the southern San Andreas fault. This scenario defines a rupture that initiates near Bombay Beach and propagates unilaterally 300 km toward the northwest. An essential feature of the source description of the ShakeOut scenario is the final slip profile along the strike of the fault defined from geological observations. We performed three sets of large-scale dynamic rupture simulations that have stochastic irregularities compatible with seismological observations and match the ShakeOut Mw. The sets of models are differentiated between them in the slip distribution characteristics as follow: The first set of models match the ShakeOut final slip profile defined as surface slip, the second set matches the final slip profile defined as depth-averaged slip, and the third set of models does not follow any ShakeOut slip profile, rather it is result of the purely stochastic input parameterization. In addition, we performed a fourth model, defined as asperity model, consistent with the calibrated dynamic rupture models proposed by Dalguer at al., 2008, BSSA. The first two sets of models are strictly ShakeOut Scenarios, as defined by The SoSAFE group, and the last two are not. Beside the wide variety of complex rupture and near source ground motion patterns between the models, the ground motion characteristics on critical areas such as Los Angeles basin are different between the ShakeOut and no-ShakeOut scenarios. The ShakeOut Scenarios predict lower ground motion than the no-ShakeOut Scenarios.

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