CAREER: Induced seismicity: Increasing understanding of fluids in fault zones and engaging stakeholders for rapid knowledge transfer

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Earthquakes occurring near oil and gas production wells have surged in number and public visibility within the US in recent years. These earthquakes may be triggered by pressure changes in subsurface rock layers resulting from injection or withdrawal of fluids, and are referred to as induced seismicity. These earthquakes pose a hazard to local residents and create challenges for energy production. However, despite recent research, we remain unable to determine, prior to injection, whether wells in a given area are likely to induce earthquakes, and if so, of what number and magnitude. This research seeks to determine the primary factor(s) controlling the triggering of induced seismicity, to test seismic methods of detection of increased fluid pressure along subsurface fault zones that may potentially increase seismic risk, and to investigate whether faults produce detectable seismic signals during the initiation of fault slip during moderate earthquakes. Results from this research will be combined with related studies to provide current and unbiased scientific information regarding induced seismicity to stakeholders, such as local residents, oil and gas regulators, oil and gas corporations, or scientists advising these groups. The results will have broad global significance for energy resource development since induced seismicity has occurred in association with wastewater disposal wells, hydraulic fracturing operations, geothermal stimulation, gas production, and gas storage. Induced seismicity is a potential challenge for long-term carbon storage in the subsurface, one of the primary solutions proposed to remove carbon dioxide from the atmosphere, thus mitigating the impacts of climate change. Results from this research may also provide insight into the processes by which fault slip initiates during earthquakes.This research will acquire seismic data using long-term and dense passive seismic networks, encompassing regions of high-volume wastewater disposal near known large faults. Data will be used to monitor the seismic or aseismic nature of pressure propagation away from active wells, and to probe the seismic responsiveness of the local faults. Forty-five broadband seismometers will be deployed at about 5 km spacing in two 18-month deployments, first in Oklahoma and subsequently in a complementary region of active fluid injection. Within the spatial footprint of the first deployment, a high-density array will be deployed over actively evolving seismicity. Specifically, the research will address 1) whether dense arrays are capable of continuously mapping pressure migration fronts away from wastewater disposal wells by detecting signals from fluid pressure migration; 2) the degree to which this migration is focused along a narrow pathway of faults/fractures, or dispersed over multiple pathways; 3) whether large fault zones are seismically reactive to the larger nearby earthquakes; and 4) whether seismic source characteristics change temporally as fluid pressure increases. The region within north-central Oklahoma includes active seismicity, large disposal wells, and a major fault system. In the second region, with a contrasting geological environment, this research will test and refine methods to detect signals of high fluid pressure approaching faults. Results from both deployments will be synthesized in the global context of induced seismicity. This research seeks to engage local residents and to help them become more confident in finding the information necessary to make informed decisions important in their lives. The scientific results will be communicated to stakeholders, within the context of a frequently updated synthesis of research completed by other groups. This work will engage next-generation leaders in the fields of hazards and resources across geoscience and engineering.