Modeling slip on rate-and-state faults induced by off-fault fluid injection

William E. Chen, Nadia Lapusta, & Xiaojing (Ruby) Fu

Submitted September 7, 2025, SCEC Contribution #14573, 2025 SCEC Annual Meeting Poster #TBD

Elevated pore fluid pressures due to fluid injection in the subsurface can induce both seismic and aseismic slip on faults. The spatial and temporal variations in pore fluid pressures experienced by the fault are in turn determined by the nature of the injection and fault structure. Most previous studies of rupture nucleation in the presence of fluid injection considered either injection directly into the fault or simplified friction constitutive laws. We present spectral boundary-integral modeling of fault slip using rate-and-state-dependent friction in the presence of evolving pore fluid pressures due to several injection scenarios and fault permeability structures. We first apply analytical solutions for fluid injection in a uniform bulk, investigating the nucleation and evolution of rupture in response to the pore fluid pressure front as it arrives on the fault. We then extend this model by implementing numerical solutions for injection in a bulk with heterogeneity in permeability due to fault architecture, including low fault-normal permeability and high along-fault permeability. We highlight the significant differences between: (i) simulations with rate-and-state friction vs. more commonly used slip-weakening laws, including the effects of healing; (ii) simulations with on-fault vs. off-fault fluid injection; and (iii) simulations with homogeneous vs. more realistic fault-zone permeability structures.

Key Words
Induced Seismicity, Modeling

Citation
Chen, W. E., Lapusta, N., & Fu, X. (2025, 09). Modeling slip on rate-and-state faults induced by off-fault fluid injection. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)