Evolution of contacting rock surfaces and a slip - andtime - dependent fault constitutive

By integrating eeects of microscopic interactions between statisticaly self-similar fault surfaces, we succeeded in deriving a slip-and time-dependent fault constitutive law that rationally uniies the slip-dependent law and the rate-and state-dependent law (Aochi and Matsu'ura, 199881]). In this con-stitutive law the slip-weakening results from the abrasion of surface asperities that proceeds irreversibly with fault slip. On the other hand, the restoration of shear strength after the arrest of fault slip results from the adhesion of surface asperities that proceeds with contact time. The slip-and time-dependent law can explain three basic experimental results; slip-weakening in high-speed slip, log t-healing in stationary contact, and velocity-weakening in steady state slip. Another interesting property expected from the uniied constitutive law is the gradual increase of the critical weakening displacement D c with stationary contact time.