Interseismic pore compaction suppresses earthquake occurrence and causes faster apparent fault loading

Abstract

Physical and chemical processes operating on faults during interseismic periods are important for earthquake generation. In this study, we focus on pore compaction within fault zones driven by chemical kinetic effects. One established model of compaction causes an increase of pore fluid pressure almost linearly with time, if fluid diffusion is neglected. We introduced it into a simple numerical model for earthquake cycles and found that this effect can drastically change the recurrence of earthquakes: (1) It gradually stabilizes the fault and eventually suppresses earthquake occurrence (2) It surprisingly causes faster "apparent" fault loading. Furthermore, we developed an expression for the "apparent" loading velocity and checked that it is consistent with the results of numerical calculations. We also extended the expression for the "apparent" loading velocity to include the effect of pore dilatancy. This "apparent" loading would not only appear in a simple elastic system with a single degree of freedom, but also in complicated systems that involve simulations of realistic earthquake cycles.