Dynamical segmentation and rupture patterns in a "toy" slider-block model for earthquakes

Lattice models for earthquakes have been shown to capture some of the dynamical properties possessed by natural fault systems. These properties include: 1) a scaling (power law) region in the curve representing event frequency as a function of magnitude and area; and 2) space-time clustering of events. To understand the physical origin of these and other effects, we examine the simplest kind of "toy" slider block model. We obtain results indicating that this model displays several additional kinds of phenomena seen in real earthquake faults, even though "realistic" physics is missing from the model. Asperity-like slip distributions in this model arise from strong elastic coupling, rather than the spatially heterogeneous frictional strength often inferred for real faults. Simulation results indicate that "characteristic" earthquakes can be produced as a consequence of the nonlinear dynamics. Thus segmentation on faults may be a result of the nonlinear dynamics as well as being due to geometric properties of fault systems. These conclusions may be modified when more "realistic" physics is added to the model, although the presence of dynamical effects in the toy model calculations similar to those observed in nature demonstates alternative possibilities for the origin of these effects.