[S-SS07] Fault Rheology and Earthquake Physics

[SSS07-P12] Dynamic earthquake sequence simulation accounting for interseismic poroelastic rebound: Postseismic fault healing dominates over poroelastic loading to a fault

*Hiroyuki Noda¹ (1.Kyoto University, Disaster Prevention Research Institute)

Keywords:Dynamic earthquake sequence simulation, Poroelasticity, Fault healing, Afterslip

Afterslip inside a coseismic slip patch is rarely observed, though some previous studies suggest that it can be driven by poroelastic rebound (PE). These studies assume constant frictional strength, whereas time-dependent strengthening (healing) of a fault is expected from laboratory experiments, which provide a basis for a rate- and state-dependent friction law (RSF). In this study, PE was implemented in a dynamic earthquake sequence simulation using a spectral boundary integral equation method, and the effect of PE on the behavior of a fault governed by RSF was examined. Spatio-temporal convolution for PE, which would significantly affect the resolution of the numerical simulation affordable, has been managed to be avoided by numerical approximation of the time dependency of Green’s function of PE in the wavenumber domain, defining memory variables, and reformulating the temporal convolution into ordinary differential equations of the memory variables. In the novel method, the additional numerical costs due to PE are negligible. A planar fault with a rate-weakening patch embedded in the rate-strengthening region was simulated. Because it is the healing of the fault that competes against PE, both the aging law and slip law were examined, which have different characteristics in the evolution of the fault strength. The simulation results indicate that PE causes postseismic loading to the patch, but the healing efficiently suppresses afterslip not only for the aging law, but also for the slip law. When cases with different friction laws are compared, the healing is more significant for the aging law, which has log-t strengthening at a limit of V=0. However, the effect of PE on the slip rate is minor for the slip law. The slip law yields additional healing if the fault is accelerated by loading owing to PE. The simulation results are consistent with the absence of afterslip within the coseismic slip patches in the observations.