Reservoir-induced seismicity (RIS) is a major concern in geo-engineering, resulting from the coupled interactions among fault mechanics, in-situ stress, and fluid flow associated with reservoir impoundment. Gaining insight into earthquake dynamics is essential for clarifying rupture processes in RIS, particularly the mechanisms governing fault reactivation and the transition from quasi-static aseismic slip to dynamic rupture. The nucleation phase is of particular interest, as it may provide critical constraints for identifying preseismic signals and estimating earthquake magnitudes.
We present a novel two-dimensional, fully coupled poro-visco-elasto-dynamic finite-element model, implemented in COMSOL, to simulate RIS under reservoir impoundment in extensional tectonic settings. Porous medium is modeled as a Kelvin–Voigt poro-visco-elastic solid to account for elastic deformation and intrinsic damping, while inertial effects are included to capture rupture dynamics and seismic wave propagation. Fault slip is simulated using non-penetrating contact surfaces enforced through an augmented Lagrangian formulation and governed by rate-and-state friction, with fault deformation accommodated via a virtual thin-layer representation.
Simulation results indicate that when frictional and hydromechanical conditions favor fault reactivation, slip may become unstable and evolve into a coseismic event. Rupture propagates along the fault in an asymmetric, two–crack-tip–like pattern emanating from the hypocenter, with higher propagation speeds in stiffer rock compared to softer material. Reservoir-induced preferential fluid flow advances rupture nucleation, while depth-dependent variations in porosity and permeability within the fault damage zone—higher than those of the surrounding rock at shallow depths—facilitate fluid migration along the fault and promote longer rupture lengths.
These results highlight the importance of mechanical and hydraulic properties in governing nucleation and rupture processes in RIS, with important implications for the design and management of reservoir impoundment.