Bimaterial effects in an earthquake cycle model using rate‐and‐state friction

Abstract

We have developed a computational framework to study earthquake cycles in 2‐D plane strain and apply it to faults separating dissimilar material. We consider a planar, strike‐slip fault governed by rate‐and‐state friction where quasi‐dynamic events nucleate spontaneously due to remote, tectonic loading. We investigate the influence of material contrast over the course of many hundreds of years. For the parameters we consider, we find that the presence of bimaterial properties influences the earthquake nucleation site, such that rupture in the preferred direction (that is, in the direction of particle motion of the side of the fault with lower shear wave velocity) is favorable. For large values of the critical slip distance Dc, events propagating in the preferred rupture direction occur for a wide range of material contrasts. For smaller values of Dc, small events emerge, even in the monomaterial case. With material mismatch present, some of these small events propagate in the nonpreferred direction, made possible by a favorable stress distribution left on the fault from previous ruptures. These results may shed light on our understanding of rupture directivity on large strike‐slip faults (like the San Andreas Fault in California) which occasionally host events rupturing in the nonpreferred direction.

Semiautomated Estimates of Directivity and Related Source Properties of Small to Moderate Southern California Earthquakes Using Second Seismic Moments

“…Simulations of bimaterial ruptures on an interface governed by slip‐weakening friction produced bilateral ruptures for various cases (e.g., Andrews & Harris, ; Harris & Day, ). However, large parameter‐space studies with slip‐weakening friction (e.g., Brietzke et al, ; Shi & Ben‐Zion, ), slip‐ and velocity‐dependent friction (Ampuero & Ben‐Zion, ) and rate‐state friction (Erickson & Day, ) showed that bimaterial ruptures tend to have preferred directivity for wide ranges of conditions. Recent high‐resolution laboratory experiments of bimaterial ruptures have led to the same conclusion (Shlomai & Fineberg, ).…”

A Novel Hybrid Finite Element‐Spectral Boundary Integral Scheme for Modeling Earthquake Cycles: Application to Rate and State Faults With Low‐Velocity Zones

“…The transitions in nonlinear rheology on fault surfaces, between rate weakening and rate strengthening, have been shown to contribute to the coseismic and interseismic slip evolution on the fault surface (Noda & Lapusta, ; Rice, ). However, off‐fault properties and bulk heterogeneities may also play a significant role in altering the earthquake cycle pattern (Cappa et al, ; Dolan & Haravitch, ; Erickson & Day, ; Lindsey et al, ). For example, ruptures that would load the bulk beyond its elastic limit, leading to the development of inelasticity or damage around the fault, may lock in nonuniform stresses on the fault surface that would impact subsequent ruptures (Erickson et al, ).…”

Dynamic and Quasi‐Dynamic Modeling of Injection‐Induced Earthquakes in Poroelastic Media

“…Simulations of earthquake rupture in complex scenarios or involving earthquake sequences often use the so-called quasi-dynamic approach (Erickson & Day, 2016;Erickson & Dunham, 2014;Douilly et al, 2015;Rice, 1993;Rice et al, 2001;Wei et al, 2013), in which inertial effects are neglected. Slip instability under quasi-static mechanics leads to unbounded slip speeds, and the singularity is resolved through a radiation damping approximation, that is, by adding a velocity-dependent cohesion that bounds the slip velocity at rupture fronts (Rice, 1993;Rice et al, 2001).…”