SLIP COMPLEXITY IN DYNAMIC-MODELS OF EARTHQUAKE FAULTS

We summarize recent evidence that models of earthquake faults with dyn amically unstable friction laws but no externally imposed heterogeneit ies can exhibit slip complexity. Two models are described here. The fi rst is a one-dimensional model with velocity-weakening stick-slip fric tion; the second is a two-dimensional elastodynamic model with slip-we akening friction. Both exhibit small-event complexity and chaotic sequ ences of large characteristic events. The large events in both models are composed of Heaton pulses. We argue that the key ingredients of th ese models are reasonably accurate representations of the properties o f real faults.