Stress analysis and rupture dynamics of the 2019 Ridgecrest Sequence

Jordan Cortez, David D. Oglesby, Christodoulos Kyriakopoulos, Baoning Wu, Abhijit Ghosh, & Roby Douilly

Submitted August 15, 2020, SCEC Contribution #10707, 2020 SCEC Annual Meeting Poster #075

Stress transfer from long-term loading as well as prior earthquakes can initiate seismic triggering and strongly affect rupture propagation and slip patterns in a fault system. A prime example of this effect is the 2019 Ridgecrest earthquake sequence, which consists of multiple complex conjugate fault ruptures with delayed rupture triggering. On July 4th, 2019 a M6.4 earthquake took place in California, resulting in left lateral surface ruptures as well as slip on a buried right-lateral conjugate fault. Approximately 30 hours later an M5.4 earthquake ruptured ~10km northwest of the M6.4 hypocenter, then 6 hours later an M7.1 main shock occurred almost 2 km west of the M5.4 event. In this study, we utilize 3D finite element dynamic rupture models to explore the rupture propagation pattern in the M6.4 foreshock, with a special focus on the influence of time-dependent stress transfer on seismic triggering on this system with complex fault geometry. Dynamic rupture models are extremely sensitive to the fault geometry, so our model is constrained by both observed surface ruptures and aftershock data. Our results suggest that only a narrow range of fault stresses, fault burial depths, and hypocenter locations would result in the observed rupture path in the M6.4 event. Our study illustrates that rupture propagation from one fault to another is strongly dependent on the level of overall stress as well as the details of fault geometry, including depth of fault burial. Investigating the physical mechanisms associated with this seismic domino effect will improve our knowledge regarding fault interactions.

Cortez, J., Oglesby, D. D., Kyriakopoulos, C., Wu, B., Ghosh, A., & Douilly, R. (2020, 08). Stress analysis and rupture dynamics of the 2019 Ridgecrest Sequence. Poster Presentation at 2020 SCEC Annual Meeting.

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