A Spectral Boundary‐Integral Method for Faults and Fractures in a Poroelastic Solid: Simulations of a Rate‐and‐State Fault With Dilatancy, Compaction, and Fluid Injection

Fluid-fault interactions result in many two-way coupled processes across a range of length scales, from the micron scale shear zone to kilometer slip patch. The separation and complex coupling render fluid-fault challenging simulate, yet they are key for our understanding experimental data induced seismicity. Here we present spectral boundary-integral solutions in-plane interface sliding opening poroelastic solid. We solve fault presence rate-and-state frictional properties, inelastic dilatancy, injection, diffusive bulk. localization is treated as having finite width non-constant pore pressure, albeit with simplified mathematical representation. dimension 2D plane strain problem reduced 1D resulting increased computational efficiency incorporation small-scale shear-zone physics into boundary conditions. apply method injection experiment that has been previously studied modeling. explore influence bulk response, diffusivity addition dilatancy on during injection. Dilatancy not only alters drastically stability but also nature pressure evolution fault, causing significant deviation standard square-root-of-time diffusion. More surprisingly, varying bulk's response (by using different values undrained Poisson's ratio) hydraulic can be critical determining rupture dilatancy.