Lei Jin

We present a new method for modeling fluid-perturbation induced seismicity in a fluid-saturated poroelastic medium embedded with a dual network of fractures. The inter-seismic triggering is deterministically modeled using a quasi-static, nonlinear and fluid-solid fully coupled fracture-poro-mechanical approach that resolves only the large-scale fractures. The co-seismic dynamic rupture is not explicitly modeled. Instead, the seismicity-induced shear stress drop is approximated as a static quantity and stochastically modeled on a range computed from the evolving poroelastic stress in conjunction with the initial stress and the static and dynamic frictional strengths. These two steps are sequentially connected and then iterated via a prediction-correction type of fracture stress updating scheme, naturally producing repeating seismic events on certain fractures. As an example, we perform three progressive numerical experiments. By comparing the corresponding synthetic event catalogs, we investigate the effects of fractures and poroelastic coupling on the evolution and source characteristics of the seismicity. Main findings include (1) the seismicity clusters near large-scale fractures favorably oriented and subjected to sufficient perturbations, (2) poroelastic coupling enhances the clustering and substantially inhibits the seismicity in the nearfield and (3) source characteristics and the b-value seem not affected by fractures or poroelastic coupling. Our method can serve as a general physics-based tool for more realistically predicting induced seismicity in complex geological media.