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Wastewater disposal linked to earthquakes
The number of earthquakes is increasing in regions with active unconventional oil and gas wells, where water pumped at high pressure breaks open rock containing natural gas, leaving behind wastewater in need of disposing. Keranen et al. show that the steep rise in earthquakes in Oklahoma, USA, is likely caused by fluid migration from wastewater disposal wells. Twenty percent of the earthquakes in the central United States could be attributed to just four of the wells. Injected fluids in high-volume wells triggered earthquakes over 30 km away.
Science, this issue p. 448
Unconventional oil and gas production provides a rapidly growing energy source; however, high-production states in the United States, such as Oklahoma, face sharply rising numbers of earthquakes. Subsurface pressure data required to unequivocally link earthquakes to wastewater injection are rarely accessible. Here we use seismicity and hydrogeological models to show that fluid migration from high-rate disposal wells in Oklahoma is potentially responsible for the largest swarm. Earthquake hypocenters occur within disposal formations and upper basement, between 2- and 5-kilometer depth. The modeled fluid pressure perturbation propagates throughout the same depth range and tracks earthquakes to distances of 35 kilometers, with a triggering threshold of ~0.07 megapascals. Although thousands of disposal wells operate aseismically, four of the highest-rate wells are capable of inducing 20% of 2008 to 2013 central U.S. seismicity.