Hydraulic Fracturing Enhances Wastewater Disposal Seismicity in Eastern Oklahoma

Between June 2019 and June 2022, 1192 earthquakes of magnitude ML 0.2–3.7 were recorded by the Oklahoma state seismic network near the town of Quinton in eastern Oklahoma. In our analysis of the area, we find that the earthquake sequence was plausibly enhanced due to adjacent hydraulic fracturing (HF) activity that broadened the influence of wastewater injection at a single disposal well. The initial cataloged seismicity indicated earthquake epicenters aligning as a northeast-striking fault south of northeast-striking mapped faults. However, careful relocation suggests the seismicity epicenters overlay a series of east–west-striking faults that are subparallel to the maximum-horizontal stress direction. We reanalyze the seismicity to establish the interaction between HF and wastewater disposal (WD) and their role in inducing seismicity in the area. We relocated earthquakes using a double-difference scheme and a local 1D velocity model to reveal three fault segments oriented in a northwest direction. The spatiotemporal occurrence of seismicity suggests increased pore pressure from the point of injection as the primary driver of seismicity. HF is found to “prime” the faults for the WD to induce and propagate seismicity. Furthermore, the preceding HF may have increased the vertical hydraulic connectivity, allowing a direct vertical propagation of fault permeability. The frequency-index method, which utilizes earthquake waveform frequency content, indicates fluid inclusion into the seismogenic faults during the fault reactivation by wastewater injection.