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Using Dynamic Rupture Simulations to Investigate the Effects of Topography on Rupture Propagation Along Branch Faults: Implications for the San Andreas and Garlock Faults

Description: 

The San Andreas (SAF) and Garlock (GAF) fault intersection in Southern California represents the juncture of California's two longest faults. Paleoseismic studies suggest this section of the SAF has hosted some of the largest earthquakes in California (M 7.9 1857 Fort Tejon Earthquake) with an estimated recurrence interval of 100-150 yrs for M > 7 events. Therefore, determining whether rupture will stop or propagate through this juncture is vital to the estimation of seismic hazard. Numerical models of branch faults have described many factors that affect the ability of rupture to propagate through discontinuities. Many branch fault systems are located in regions with asymmetric topography. Previous dynamic studies investigating the effect of asymmetric topography on a single fault have demonstrated that topography causes normal stress perturbations during rupture. Thus, considering the irregular topography at the SAF-GAR junction, it is worth investigating whether this topography has any effect in influencing rupture to propagate or not past the branch intersection. In this work we first run simple planar models with 5 different synthetic topographies to isolate the effects of topography on the rupture process on branch faults. Our results indicate that topography can introduce dynamic clamping and unclamping phases during the rupture which can lead to different rupture behavior at the branch intersection. We then consider a more realistic fault model of the SAF-GAR intersection with the actual topography. In this simulation, consistent with the simple models, our result shows that incorporating real topography leads to different rupture behavior in comparison to a model with no topography. This suggests that although dynamic phases are smaller in magnitude than static stress changes, they could be sufficient to cause failure if the branch is weak. We plan to further investigate this by considering a variety of on fault stresses as well as nucleation location.

Session: Numerical Modeling in Seismology: Developments and Applications [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Evan Marschall

Student Presenter: Yes

Invited Presentation: 

Authors