Mitigating injection-induced seismicity to reduce seismic risk

Over the past decade, parts of the central United States have experienced elevated number of earthquakes and seismic damage to buildings and infrastructure. These earthquakes are caused by underground injection of wastewater from oil and gas operations, which increases pore pressures, in some cases leading to slip on faults in the geologic basement. Mitigation strategies have been proposed or implemented to reduce these earthquakes, while minimizing impact on operations, but the effectiveness of these strategies in terms of seismic risk is not well understood. Here, we show that the most effective strategies for reducing earthquake occurrence may not be the best for reducing regional seismic risk in terms of economic loss. Well locations have a large impact on seismic risk, and increasing the distance between wells typically reduces risks, with the least interruption to injection operations. Results also quantify the dramatic decrease in risk achieved by locating injection operations farther from population centers. Decreasing injected volume reduces both earthquake occurrence and risk, but large reductions in volumes are needed to achieve significant reductions in risk. These findings can be used to inform design and selection of mitigation strategies that most reduce seismic risk.