NUMERICAL-SIMULATION OF EARTHQUAKE FAULTS WITH GOUGE - TOWARD A COMPREHENSIVE EXPLANATION FOR THE HEAT-FLOW PARADOX

The particle-based lattice solid model is used to simulate transform f aults with and without fault gouge. Stick-slip frictional behavior is observed in two-dimensional numerical experiments of model faults both with and without gouge. When no gouge is present,the fault is strong, and the heat generation and stress drops are correspondingly high, in disaccord with observations surrounding the heat flow paradox. In con trast, when a gouge is specified, the fault is weak, and the heat gene ration as well as stress drops are low, in quantitative agreement with observational constraints. The heat flow is low on average and during short periods of aseismic creep. Seismic efficiencies are compatible with observationally based bounds. Counter intuitively, the fault stre ngth decreases as the intrinsic friction between particles is increase d beyond a given threshold. The mechanism for low fault strength and h eat is rolling and jostling of fault gouge grains during slip. This al lows macroscopic movement of the fault with only minimal slip between surfaces of the gouge grains. As this dynamical mechanism operates dur ing seismic and aseismic slip, it provides an explanation for the lack of a heat flow anomaly in both the seismic and creeping parts of the San Andreas fault. The simulation results provide the first comprehens ive and quantitative possible explanation of the heat how paradox and suggest that fault gouge plays a fundamental role on the dynamics of e arthquake faults. Whether rolling and jostling of fault gouge particle s provides the explanation for the heat flow paradox in nature remains to be validated by observation evidence.