FAULT STRUCTURE IN THE PAWNEE AREA AND ITS IMPLICATIONS FOR EARTHQUAKES

The 2016 Mw 5.8 Pawnee earthquake is the strongest earthquake on record in Oklahoma. Surrounded by several injection wells, the Pawnee earthquake is believed to be triggered by the interplay between wastewater disposal and foreshocks, which reactivated the pre-existing subsurface fault system. To better understand the nonlinear relation among the fluid injection, fault system, and seismicity in the region, we obtain high-resolution velocity structure and earthquake locations in the Pawnee area. The high-resolution velocity model characterizes the fault geometry and dimensions, revealing subsurface faults and providing constraints on rupture sizes. Meanwhile, the high-resolution relocated seismicity catalog aids in the detailed characterization of faults and precursory events. Our study provides strong seismic constraints on the rock properties and fault system beneath the Pawnee region, indicating a complex interaction among fluid injection, tectonics, and seismicity that jointly derives the fault evolution in this region.