Effect of Permeability Evolution in Fault Damage Zones on Earthquake Recurrence

Micro-crack density, porosity, and permeability in fault damage zones play an important role in the pore fluid diffusion process. During long-term earthquake cycles, those properties change with time as a result of either physical damage or chemical/physical healing. Hence, the evolution of permeability can affect the recurrence of earthquakes by either delaying or accelerating the weakening of the fault core through controlling the pore pressure distribution and changing the effective normal stress. In this study, we use a single degree of freedom spring slider analog fault model to simulate the earthquake sequences, considering permeability as a decreasing function of the effective normal stress and thus an increasing function of pore pressure; we also examine its evolution resulting from coseismic damage and interseismic healing. Our simulation results show that different permeability evolution, controlled by various physical conditions, could result in a variety of fault slipping histories, which demonstrates the importance of incorporating the permeability evolution into earthquake modeling, especially when assessing the long-term effects.