Mechanical model of an earthquake fault

Abstract

We examine the dynamic behavior of a simple mechanical model of an earthquake fault. This model, introduced originally by Burridge and Knopoff [Bull. Seismol. Soc. Am. 57, 341 (1967)], consists of an elastically coupled chain of masses in contact with a moving rough surface. Our version of the model retains the full Newtonian dynamics with inertial effects and contains no externally imposed stochasticity or spatial inhomogeneity. The only nonlinear feature is a velocity-weakening stick-slip friction force between the masses and the moving surface. This system is being driven persistently toward a slipping instability and, therefore, exhibits noisy sequences of earthquakelike events. We observe these events in numerical simulations and are able to predict many of their features analytically. Their size distributions are found numerically to be consistent with the Gutenberg-Richter law. Some aspects of the size distributions can be understood by scaling arguments.