Pore Pressure Perturbations on Rough Fault Earthquake Cycle Simulations

Induced seismicity has become common, and efforts to understand, reduce, and mitigate the associated risks call for modeling and observations. We performed 2D elastic earthquake cycle simulations on geometrically rough faults with spatially uniform velocity-weakening friction. We simulate fluid injection by increasing the pore pressure at a constant rate of 0.1 MPa/yr, which in turn decreases the effective normal stress. Pressurization was initiated at various times through the unperturbed earthquake cycle, which has a duration of ∼500 yr. Ambient effective normal stress is chosen to correspond to hypocentral depths in the central United States. Our simulations show interplay between slow slip, creep, and foreshocks leading to whole fault ruptures. Unsurprisingly, the pressure perturbation and time to system-spanning ruptures decrease with time in the earthquake cycle. However, the pressure change to the first postinjection foreshock, and between the first foreshock and the mainshock, shows much greater variability. This suggests seismicity onset may be a poor predictor of time to full rupture.