Coulomb Stress Transfer Influences Fault Reactivation in Areas of Wastewater Injection

Abstract

We explore the role of Coulomb stress transfer in the fault reactivation in Woodward, Oklahoma—a wastewater injection area. We address this issue by first defining fault segments from earthquake spatiotemporal clustering then parameterizing the geometries of each segment by combining seismicity and focal mechanisms. Finally, we calculate Coulomb stress transfer along each fault segment. Our results reveal a fault system characterized by a flower structure with strike-slip fault at deeper depth and distributed normal faults at shallower depth. Further, Coulomb stress analysis reveals that the fault reactivation initiates at the fault bend and sequentially migrates to northeast and southwest due to interevent stress interaction. The amplitude of Coulomb stress transfer is at least comparable to pore pressure and poroelastic stress changes estimated from fluid injection. Overall, our observations suggest that fault structure and Coulomb stress transfer constitute important factors in seismogenic fault reactivation within areas of wastewater injection.