Group , Poster #142, Fault and Rupture Mechanics (FARM)

Stress transfer and fault geometry's influence on the 2019 Ridgecrest Earthquake slip distribution

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

2021 SCEC Annual Meeting, Poster #142, SCEC Contribution #11379 VIEW PDF
Stress transfer from long-term loading as well as prior earthquakes can lead to seismic triggering and strongly affect subsequent rupture propagation and slip patterns in a fault system. A prime example of this effect is the 2019 Ridgecrest earthquake sequence, which consisted of multiple complex conjugate fault ruptures with delayed rupture triggering. On July 4th, 2019 an M6.4 earthquake produced left lateral surface ruptures as well as slip on a buried right-lateral conjugate fault. Approximately 30 hours later an M5.4 earthquake occurred ~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 rupture propagation’s influence on slip patterns and its corresponding induced stress to neighboring faults within a system of complex fault geometry, including all three major events in this rupture sequence. We compare models with different initial stress conditions to better understand how complex geometry and stress can influence rupture propagation, and hence overall slip patterns. These effects are extremely sensitive to the fault geometry, so our models are constrained by both observed surface ruptures and aftershock data. Our results suggest both homogenous and heterogenous initial stress models of the M7.1 main shock produce heterogenous slip for that event, but the latter model produces slip patterns that agree more with geodetic models. Both models illustrate the influence fault geometry has on rupture propagation, with varying slip patterns near bends and fault intersections. Overall, our study illustrates that rupture propagation from one fault segment to another is strongly dependent on the level of overall stress as well as the details of fault geometry. Investigating the physical mechanisms associated with this seismic “domino effect” will improve our knowledge regarding fault interactions and help estimate their effects in potential future events.
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