The Effect of Aseismic Slip on the Timing and Size of Induced Seismicity

Date: 4/26/2019

Time: 08:45 AM

Room: Cascade I

The key to effective hazard mitigation of induced seismicity is a thorough understanding of the triggering mechanisms of induced earthquakes. Apart from the direct effect of fluid present on the fault and the change in loading due to poroelastic stresses, recent studies also suggested complex driving forces that involve aseismic motion on the fault. The interplay of seismic and aseismic motion in the context of induced seismicity is particularly intriguing because of the complex interaction among fluid, frictional fault interface and the evolving state of stress during and after the injection.

In this study, we simulate the aseismic motion on a fault that is subjected to fluid-induced stress perturbation. The fault is subjected to various levels of poroelastic-stress or pore-pressure perturbations that occur at different times during a selected seismic cycle. We consider the effects of aseismic slip on both the timing and size of the induced seismic events. One observation from our numerical results is that the induced aseismic response on the fault can either advance and delay the next seismic event, i.e. it is capable of both stabilizing and destabilizing the fault. In particular, the delaying in triggering tends to happen when the level of stress perturbation is low (0.1 – 0.2 MPa) and when the perturbation occurs late in the interseismic period. Our model shows that the state of stress of the fault at the moment of perturbation and the critical nucleation size of the fault are important factors that control the extent of aseismic response on the fault and timing of the triggered event.

Our ongoing work is to better quantify the aseismic response caused by different types of induced stress perturbation and to investigate the aseismic response of faults in subsequent earthquake cycles. We aim to better constrain the range and timing of stress perturbations that are favorable for inducing earthquakes. The subsequent step is then to incorporate specific fluid injection histories and fault frictional properties to model field observations.

Presenting Author: Semechah K. Y. Lui

Authors