Seismicity induced by fluid migration in the Main Ethiopian Rift

In the last years a large amount of geological, geophysical and seismological data have been produced by induced seismicity studies. These studies have given a great contribute to the understanding of the physical processes triggered by the fluid-structure interaction in active fault zones. Frictional laboratory experiments on fault rock samples have shown that the style of deformation (e.g. stick-slip or aseismic creeping) can change in presence of fluids. In addition, high-precision seismicity locations coupled with the interpretation of high-resolution seismic profiles have allowed to understand the time-spatial evolution of the permeability inside complex fault systems. Here we integrate different data available from the literature to model the stress perturbations induced by wastewater injection in the Val d’Agri oil field by coupled fluid flow and geomechanical numerical simulations. We model the behaviour of main faults involved in the induced seismicity process by frictional contacts in a finite element framework. The permeability into the fault zones are changed in order to understand the role of these structures either as fluid pathways or as efficient compartmentalization barriers for the pore pressure diffusion front associated to wastewater injection. To do this a fault zone model that considers the spatial variation of the hydromechanical properties from the damage zone to the fault core has been implemented in the numerical code. Final aim is to have a more complete picture of the induced seismicity in Val d’Agri oilfield as a consequence of the pore pressure increase as well as its relationship with the deformation style of the fault system and the active stress field.