Nucleation and Arrest of Fluid-Induced Aseismic Slip

Microseismicity associated with fluid pressurization in the subsurface occurs during fluid injection but can also be triggered after injection shut-in. Understanding the extent and duration of the post-injection microseismicity is critical to limit the risk of fluid-induced seismicity and insure the safe utilization of the subsurface. Using theoretical and numerical techniques, we investigated how aseismic slip on a fault plane evolves and stops after a fluid pressurization event. We found that the locking mechanisms controlling the arrest of aseismic slip highly depend on the initial fault stress criticality and the pressurization duration. The absolute arrest time of fault aseismic slip after injection shut-in is proportional to the pressurization duration and increases significantly with the initial fault stress criticality. Given that microseismicity can be triggered by aseismic slip, these results provide insights into the mechanics controlling the arrest of microseismicity after fluid pressurization as a milestone toward induced seismicity mitigation strategies.