ROLE OF FLUID INJECTION ON EARTHQUAKE SIZE IN DYNAMIC RUPTURE SIMULATIONS ON ROUGH FAULTS

Earthquakes can be induced or triggered by fluid injected deep underground. An outstanding question regarding earthquakes induced in this way is whether the volume of injected fluid and/or the spatial extent of the resulting pore pressure and stress perturbations limit rupture size. Previous studies of induced seismicity have suggested that the maximum magnitude earthquake scales with total volume of injected fluid. However, this is not always the case, and the level and heterogeneity of preexisting stress on faults likely plays an important role in determining the final earthquake size. We used numerical simulations of earthquakes to quantify one source of stress heterogeneity—that arising from geometric roughness—and study how changes in pore pressure and stress from fluid injection interact with preexisting stress to influence earthquake size. We simulate ruptures with and without injection‐induced pore pressure perturbations, using 2‐D dynamic rupture simulations on rough faults. We find that earthquakes are often not limited by the injected volume, except under specific conditions. Instead, earthquakes stop where preexisting conditions are unfavorable for continued rupture; in our case because of bends in the fault geometry. Earthquakes can exceed the predicted maximum magnitude, depending on the preexisting stress on the fault, how rough it is, and the magnitude and extent of the perturbation from injection. Future work should further develop methodology for simulation of the entire loading, initiation, and rupture stages to advance understanding of injection‐induced ruptures.

Maurer, J., Dunham, E. M., & Segall, P. (2020). Role of fluid injection on earthquake size in dynamic rupture simulations on rough faults. Geophysical Research Letters, 47, e2020GL088377. https://doi.org/10.1029/2020GL088377