The Role of Dilatancy in Fluid-Induced Fault Slip

Stacy Larochelle, Nadia Lapusta, & Jean-Paul Ampuero

Submitted August 15, 2017, SCEC Contribution #7637, 2017 SCEC Annual Meeting Poster #188

Numerous industrial activities (e.g., hydraulic fracking, wastewater disposal and enhanced geothermal systems) involve fluid injections into the crust. That these anthropogenic fluid injections have the potential to induce fault slip has been known for decades. When injected directly into a fault system, fluids decrease fault strength by increasing pore pressure. This strength drop may in turn result in seismic or aseismic slip if the ambient stress field exceeds the strength of the fault. What conditions promote stable vs. unstable failure and the exact physical mechanisms at play are still poorly understood. The present study investigates these questions through numerical models.

We simulate fluid injections into a rate-and-state fault embedded in a homogeneous medium with the elastodynamics boundary-integral code developed by Lapusta et al. [2000] supplemented with fluid diffusion along the fault. The geometry and parameters of the model are informed by the experimental field study by Guglielmi et al. [2015] in which water was pumped into a natural fault. During the injection, Guglielmi et al. observed an episode of aseismic slip followed by a sequence of microseismic events. By comparing these experimental results to our numerical simulations we hope to establish what caused the aseismic-seismic slip sequence and whether dilatancy (as described by Segall and Rice [1995]) played an important role in promoting the initially stable failure.

Larochelle, S., Lapusta, N., & Ampuero, J. (2017, 08). The Role of Dilatancy in Fluid-Induced Fault Slip . Poster Presentation at 2017 SCEC Annual Meeting.

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