Experimental and Numerical Modeling of Earthquake Rupture Interactions Across Multiple Asperities and Barriers
Yudong Sun
Stanford University
- Date & Time
- Location
- Online-only seminar via Microsoft Teams
- Summary
Natural faults are frictionally heterogeneous, containing lithological contrasts across multiple spatial scales, which can give rise to a complex interplay between fast and slow slips. A common modeling framework to explore seismicity patterns consists of velocity-weakening asperities that host seismic slip and velocity-strengthening regions that act as barriers to rupture. Earthquake ruptures are sometimes observed to propagate across barriers and sequentially break multiple asperities, resulting in large events. However, the conditions that allow such multi-patch ruptures remain poorly understood. In this study, we perform laboratory experiments on 760 mm-long Poly(methyl methacrylate) PMMA frictional interface with three velocity-weakening (VW) patches (bare PMMA) separated by velocity-strengthening (VS) barriers coated by Teflon. We reproduce these experimental results using quasi-dynamic and fully-dynamic numerical simulations with rate-and-state friction. Our results show a transition from intermittent single-patch ruptures to faster multi-patch ruptures when the nucleation size is sufficiently small or the VS barrier size is sufficiently large relative to the VW asperity size. Fully-dynamic simulations, which incorporate seismic wave propagation, allow ruptures to more easily overcome barriers and better capture the observed rupture size and speed compared to quasi-dynamic simulations. This study demonstrates a possible mechanism for the occurrence of large earthquakes and the propagation of slow slip, underscoring the critical role of seismic waves in complex ruptures across heterogeneous faults.