Dynamic Rupture Scenarios of Large Earthquakes on the Hayward, Rodgers Creek, and Calaveras Faults

Ruth Harris, USGS

Wednesday, March 24, 2021 at 10:30 AM

Online-only seminar via Microsoft Teams

The San Francisco Bay area’s Hayward fault produces large earthquakes, with the last occurring in 1868. We use dynamic rupture modeling to numerically simulate large earthquakes on the Hayward fault and its connected companions to the north and south, the Rodgers Creek and Calaveras faults. We incorporate information about this fault system’s 3D geology and 3D geometry, and inferences about its interseismic creep-rate pattern and rock-friction behavior, into a finite-element computer code to perform 3D dynamic earthquake rupture simulations. We find that crucial factors controlling rupture behavior in our models are the earthquake nucleation locations, the fault geometry, and the data that reveal where the fault system is creeping or locked. Our findings suggest that large Rodgers Creek-Hayward-Calaveras-Northern Calaveras (RC-H-C-NC) fault-system earthquakes may result from dynamic rupture that starts in a locked part of the fault system, but is then stopped by creeping parts, leading to high-magnitude-6 earthquakes; or, from dynamic rupture that starts in a locked part of the fault system, then cascades through some of the creeping parts, leading to magnitude-7 earthquakes.

Harris, R. A., Barall, M., Lockner, D. A., Moore, D. E., Ponce, D. A., Graymer, R. W., Funning, G., Morrow, C. A., Kyriakopoulos, C., and Eberhart-Phillips, D. (2021). A geology and geodesy based model of dynamic earthquake rupture on the Rodgers Creek-Hayward-Calaveras fault system, California. Journal of Geophysical Research: Solid Earth, 126, e2020JB020577. https://doi.org/10.1029/2020JB020577

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