Effect of fault roughness on injection-induced seismicity

We present a new fault injection model for induced seismicity in the context of geothermal systems. The characteristic and novelty of our model is that it is both (1) fast and thus allows a probabilistic assessment and (2) purely physic-based in the sense that none unconstrained engineering approach to mimic processes or parameters distributions are used. Our novel approach starts from the most constrained heterogeneous ingredient of the rupture model, that is the geometrical roughness of fault surfaces. Synthetic fractal surfaces mapping real fault geometry are combined with an “instantaneous” slip-weakening model with spatially homogeneous static and dynamic friction coefficients. A rich seismicity’s dynamic emerges from the non-trivial interplay between pore pressure diffusion, geometrical heterogeneities of the fault surfaces and stress interactions between the successive rupture events. Solely introducing geometrical heterogeneities as observed for natural faults can explain (1) the occurrence of rupture events at large distance from the injector and (2) the persistence in seismicity post shut-in.