Seismicity front induced by fluid injection on rough faults

The rise in frequency and magnitude of anthropogenic earthquakes has raised public concern and underscored the importance of understanding subsurface processes and mechanisms to assess induced seismic hazards and risks. While faults are ubiquitously rough, and the characteristics of fault roughness are well investigated and constrained by natural observations, the interplay between roughness and successive rupture events in induced seismicity remains poorly understood. Here, we simulate seismicity induced by fluid injection on a self-affine rough fault. The model assumes instantaneous weakening from static to dynamic friction, homogeneous friction coefficients, and instantaneous frictional healing after each earthquake. We investigate how pore pressure diffusion, initial stress state, and fault roughness influence the stress distribution and the seismicity front. We find that fault roughness significantly alters the statistical distribution of distance to failure (critical pressure), transitioning from an approximately normal distribution at low roughness to a highly skewed distribution at high roughness. Furthermore, models with similar initial stress distributions have comparable seismic fronts, highlighting the critical influence of pre-existing stress conditions. With additional simplifications, the seismicity front and back-front can be predicted reasonably well based on the initial stress distribution and the spatio-temporal evolution of pore pressure. This provides a basis for understanding additional factors such as stress interactions and spatial correlation that influence the seismicity front.