Lateral growth of the fault damage zone as a result of induced seismicity

Geo-energy applications such as geologic carbon storage, geothermal energy extraction, and subsurface energy storage, imply fluid injection and production resulting in pressure and temperature diffusion. Consequent changes in the initial hydraulic and thermal state may induce seismicity, usually nucleated at faults that cross the injection formation. Through fully coupled hydro-mechanical simulations, we investigate the fault stability affected by fluid injection into a porous aquifer that is overlaid and underlain by low permeable clay-rich formations. We find that aquifer pressurization as a result of fluid injection causes significant stress changes around the fault. Simulation results show that the least stable situation occurs at the contact between the aquifer and the fault damage zone – unexpectedly not within the fault. Induced earthquakes are likely to nucleate on the edge of the fault damage zone, leading to a lateral growth of the damage zone and a possible spreading of the fault zone.V.V. would like to acknowledge funding from the European Research Council (ERC) under European Union’s Horizon 2020 research and innovation programme (grant agreement No 801809)Peer reviewe