The role of pore fluid pressure variations in influencing seismic and aseismic fault slip remains a major challenge in earthquake mechanics. In this study, we employ the Hydro-Mechanical Earthquake Cycle (H-MEC) code to simulate fluid-driven earthquake cycles in a fully coupled solid-fluid continuum framework. The code incorporates a non-linear, plastic strain-rate dependent dilatancy-compaction formulation to explore the interplay between shear induced (de)compaction, fluid pressurization, and fault dilation. Our results demonstrate a diverse range of seismic slip behaviors, including fast dynamic rupture, slow slip transients, and stable aseismic creep. During seismic slip events, pore fluid pressurization reduces both fault shear strength and resistance to compaction, facilitating dynamic rupture as a solitary pore pressure wave. We find that fault hydraulic properties, such as porosity and permeability, critically govern slip dynamics by controlling the temporal evolution of fluid pressure transients and effective stress. We also find that shear-induced dilatancy plays a role in the long-term stabilization of the fault, while compressibility has a significant influence on the initial response of the fault, deciding whether the fault hosts seismic or aseismic slip. Our findings emphasize the importance of incorporating realistic hydro-mechanical processes in models, to explore the evolution of fluid pressure, (de)compaction and dilatancy, and their impact on the seismic slip modes.
Hegyi et al. (Thu,) studied this question.