Pore‐Pressure Cycles and Slow Slip Generation on Mildly Velocity‐Weakening Faults

Abstract

Recent observations have revealed pore‐fluid pressure fluctuations correlated with the occurrence of slow slip events (SSEs) in several subduction zones. These fluctuations, caused by fluid accumulation and migration before and during SSEs, may modulate the timing and characteristics of these events. To test whether pore‐pressure changes can induce SSEs comparable to observations, we develop a physical model in which periodic changes in pore‐fluid pressure are imposed on a planar velocity‐weakening fault by varying the effective normal stress (one‐way coupling). Fluid is assumed to be injected at the center of the fault and to diffuse along the fault plane according to the axisymmetric diffusion equation. Our results show that these perturbations produce a spectrum of slip behaviors, from quasi‐periodic SSEs to earthquakes, including mixed behaviors. The induced SSEs have durations and magnitudes ranging from approximately 3 months to over a year and Mw ${\mathrm{M}}_{\mathrm{w}}$ 5.5–7.5. However, the model does not reproduce the full range of SSE properties observed in subduction zones, and the parameter space leading to SSEs is narrower than that of models with velocity‐strengthening faults. These findings support the previously proposed idea that SSEs are more consistently reproduced by models of velocity‐strengthening faults than by models of velocity‐weakening faults subjected to pore‐pressure perturbations.