[S09-1] Open session: Earthquake generation process – physics, modeling and monitoring for forecast I

[S09-1-03] Synchronization and chaotic behavior of earthquake cycles in a model with interacting fault patches

^○Naoyuki Kato (Earthquake Research Institute, University of Tokyo, Tokyo, Japan)

Numerical simulations are conducted to investigate the effect of interacting fault patches on complex earthquake cycles. In the model, circular patches of steady-state velocity-weakening frictional property are embedded on a planar fault in uniform elastic medium, and shear loading with a constant slip rate is applied to the fault. When a single isolated velocity-weakening patch exists on a fault plane, earthquakes repeatedly occur in the patch at a constant recurrence interval in usual cases. When two or three patches exist, earthquakes on the patches are synchronized with each other for cases where natural recurrence intervals of the patches are almost the same or close to integer multiple, resulting in single- or multi- periodic earthquake occurrence. In other cases, earthquake cycles tend to be chaotic, where the time intervals between successive earthquakes vary and no periodicity is found. Chaotic behavior of earthquake cycles is observed also for cases where slip in a velocity-weakening patch changes from seismic to aseismic. In these chaotic earthquake cycles, long-term forecast of earthquakes is impossible in strict sense. However, statistical property of earthquake recurrence can be used for probabilistic forecasts. An iteration map of the recurrence intervals of simulated earthquakes in chaotic pattern is expressed by a simple curve, indicating that the timing of an event is predictable from the previous time interval, and the sequence of slip events exhibits deterministic chaos.