Friction, Fracture, and Earthquakes

A primary goal in seismology is to identify constraints arising from the small-scale physics of friction and fracture that can provide bounds on seismic hazard and ground motion at the fault scale. Here, we review the multiscale earthquake rupture problem and describe a physical model for the deformation of amorphous materials such as granular fault gouge. The model is based on shear transformation zone (STZ) theory, a microscopic model for plastic deformation. STZ theory ties fault weakening to the evolution of an effective temperature, which quantifies configurational disorder and captures the spontaneous formation and growth of narrow shear bands in the fault gouge.