CO2 storage for the energetic transition: geomechanical modeling and laboratory experiments

Physics-based numerical models of earthquake dynamic rupture serve as valuable tools for examining how seismic cycles respond to changes in fault physical properties. In particular, because natural fault zones are characterized by heterogeneous frictional and permeability properties, models have the potential to reproduce these heterogeneities and extrapolate a correspondent seismic behavior. Although several dynamic modeling works have been conducted there are numerous topics that remain still unanswered. The effect of fluid pressure perturbations on seismic cycles is not completely clear and also the study of how fluids may affect slip behavior and timing of the events is in its infancy. In this Thesis, I examined various aspects of earthquake dynamics, including the impact of frictional parameters and the role of fluid pressure (i.e., changes in effective normal stress) on fault slip behavior and earthquake recurrence intervals. The results, described in chapter 3, highlight the importance of fault frictional properties on earthquake recurrence time, and underline that a slight variation of fault frictional properties may significantly affect the seismic cycle. In chapter 4, the modeling integrates fluid pressure perturbations and fluid propagation along a fault, governed by the fluid diffusion equation, applied at different stages of the seismic cycle. This approach allows me to investigate the impact of fluids on fault slip behavior—whether a fault slips seismically or aseismically—and on the timing of the subsequent event. Furthermore, in chapter 5, I addressed the fluid pressure problem by reproducing both fluid pressure reduction, i.e. depletion, and fluid injection within a finite reservoir. Hence, the results presented in this thesis suggest that a good fault characterization is fundamental to better reproduce seismicity and also that fluid pressure may trigger aseismic slip even on active faults but depending on when fluid pressure is applied relative to its seismic cycle.