Geomechanical analysis of fluid injection and seismic fault slip for the M(w)4.8 Timpson, Texas, earthquake sequence

摘要

An earthquake sequence that culminated in a M(w)4.8 strike-slip event near Timpson, east Texas, the largest reported earthquake to date in that region, had previously been attributed to wastewater injection starting 17 months before the onset of recorded seismic activity. To test if this earthquake sequence can be attributed to wastewater injection, we conducted coupled poroelastic finite element simulations to assess the spatial and temporal evolution of pore pressure and stress field in the vicinity of the injection wells and to calculate the Coulomb failure stress on the seismogenic fault as a function of the permeability of the injection layer, fault orientation, fault permeability, and orientation and magnitude of the in situ stress. We find that injection-induced fault slip is plausible within the range of selected model input parameters, with slip favored by low reservoir permeability, low fault permeability, and a favorable orientation of the fault relative to the in situ stress state. Other combinations of equally plausible input parameters predict no slip within 96 months of simulated injection. Under most favorable boundary conditions for fault slip, fault slip occurs 7 months after the start of injection. Our results highlight the importance of detailed geomechanical site characterization for robust fault stability assessment prior to wastewater injection.