Asperity Model of an Earthquake

An asperity model of an earthquake that is based on the static solution for the exterior crack problem is described. The boundary integral method is used to explore both static and dynamic aspects of the model. The main features of the model include a strong asperity patch that retards motion on the fault and a weak surrounding shadow region where a displacement deficit develops. Failure commences when the stress intensity on the boundary of the asperity patch reaches a critical value, with the asperity patch failing first and causing a slip pulse to propagate out over the shadow region. The rise time of the slip on the fault and the rupture velocity are controlled by the type and amount of friction. The model is in general agreement with scaling relationships for repeating earthquakes and with waveforms from a nearby earthquake in both the time and frequency domains.