Investigating potential earthquake triggering and delay effects along the southern San Andreas fault by Lake Cahuilla level change
Qingjun Meng, Zhen Liu, & Yingdi LuoPublished September 8, 2024, SCEC Contribution #13740, 2024 SCEC Annual Meeting Poster #127
A series of large quasi-periodic earthquakes (five to seven) occurred along Southern San Andreas Fault (SSAF) during the last millennium, at an interval between ~116 and ~221 years (Philibosian et al., 2011). However, the cause for a much longer earthquake quiescence ~ 300 years, since the last event in 1700 C.E., is still puzzling. The SSAF locates beside ancient Lake Cahuilla that experiences periodic inundations and desiccations in historical time. Previous studies suggest a temporal correlation between Lake Cahuilla flooding and SSAF earthquakes, although a direct causal relationship is still in debate. In this study, we use a 3-dimensional fully dynamic earthquake cycle simulator, adopting the rate-and state-dependent friction (RSF) law on the fault plane to explore the influence of hydrologic perturbation associated with Lake Cahuilla towards modulating SSAF earthquake behavior. We consider a reference model that has realistic tectonic loading rate, fault geometry with a damage zone and observationally constrained RSF law, which produce an average earthquake recurrence interval agreeing with the observations. We then consider temporal variation of water load based on the paleo lake level record, fault pore pressure variation from Hill et al. (2023) and the dynamic stress perturbation from stepover fault movement for their triggering effects. We found that the perturbations from water loading, pore-pressure changes and nearby stepover fault movement all play an important role in modulating earthquakes but are insufficient to explain the earthquake sequence with a wide range of recurrence intervals. The prolonged earthquake quiescence since the last event is difficult to explain even taking into account long-lasting drought effect, approximated through pore-pressure reduction (thus effective normal stress increase) in simulation. Ongoing work is to explore more parameters space such as the variation in reference model earthquake recurrence intervals, alternative interpretation of paleo lake history records and the uncertainty of lake age evaluation.
Citation
Meng, Q., Liu, Z., & Luo, Y. (2024, 09). Investigating potential earthquake triggering and delay effects along the southern San Andreas fault by Lake Cahuilla level change. Poster Presentation at 2024 SCEC Annual Meeting.
Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)
