Repeating Slip Events at a Circular Asperity : Numerical Simulation with a Rate- and State-Dependent Friction Law

概要

論文の詳細を見る
I perform numerical simulation of slip process on a two-dimensional planar fault in an infinite uniform elastic medium using a rate- and state-dependent friction law. A circular patch with velocity-weakening frictional property is embedded in the fault, while velocity-strengthening frictional property is assumed in the other region. Simulation results indicate that slip events repeatedly occur at the velocity-weakening patch and slower slip propagates outwards in the velocity-strengthening region. The characteristics of simulated slip on the fault patch are controlled by the ratio of the patch radius r to the critical fault radius rc, which is the critical nucleation patch radius for unstable slip, and is defined as a function of frictional constitutive parameters. When r≫rc, ordinary earthquakes with high slip rates repeatedly occur at the fault patch and postseismic aseismic slip follows on the fault outside the patch. When r～rc, episodic aseismic slip events (silent earthquakes) occur. The rise time of the episodic event increases with a decrease in r/rc. When r≪rc, stable sliding occurs. These results indicate that the rc value can be estimated from geodetically determined values of the fault radius and the source duration of an episodic aseismic slip event.