A team of federal and university geologists have linked a series of unusual earthquakes, including a destructive 5.7-magnitude shocker, to oil-drilling wastewater-injection wells in Oklahoma.
The earthquakes occurred near Prague, Oklahoma, in 2010. The largest quake left two people injured, destroyed 14 homes, damaged a federal highway and was felt as far away as Milwaukee, according to a Columbia University release.
Columbia geologists partnered with the US Geological Survey to produce the report, which revealed a "potential" link between drilling wastewater injection and the massive earthquake.
The wells suspected of causing the earthquakes were in operation for at least 18 years, and the seismic events indicate that there can be decades-long lags between drilling wastewater injection and seismic events, according to the report.
The injection-well operations linked to the earthquakes were relatively small and involved filling oil wells with waste fluids, but over the years, pressure in the wells increased and eventually lubricated a known seismic fault.
"There's something important about getting unexpectedly large earthquakes out of small systems that we have discovered here," said Geoffrey Abers, a co-author of the study.
Abers said the team's observations indicate that the risk of humans inducing large earthquakes from even small injection activities is "probably higher" than previously thought.
The findings come at a time when geologists are reporting an uptick in minor earthquakes across the country linked to unconventional hydraulic fracturing, or "fracking." Fracking has facilitated an oil- and gas-drilling boom across the country, and the process produces large amounts of liquid waste that is most often injected into underground wells for disposal.
In the last four years, the number of earthquakes in the central United States spiked by 11 times compared with three decades prior, the authors of the Oklahoma study estimate.
The wells suspected of causing the massive quake in Oklahoma were not disposing of unconventional fracking waste, but the report raises new concerns about the long-term impacts of underground drilling-waste disposal.
Oklahoma state officials have not officially determined the source of the earthquakes. In response to the report, a state geologist said the findings could link the wells to earthquakes, but the Oklahoma Geological Survey still suspects that they were naturally occurring, according to the Columbia University release. Well operations continue at the site.
Every day, the oil and gas industry injects two billion gallons of liquid waste into any number of 144,000 underground wells, according to the US Environmental Protection Agency. Earthquakes related to wastewater injection are rare, but in recent years, fracking-waste-injection wells have been linked to earthquakes in several states, including Ohio, Alabama, Arkansas and California.
Between the spring of 2011 and early 2012, a fracking-waste-injection well caused more than a dozen minor earthquakes near Youngstown, Ohio, including one 4.0 magnitude earthquake that was felt for miles.
A Truthout investigation found that Ohio regulators permitted operators of the Ohio well to raise its maximum injection pressure twice, once shortly before and once again after the well-caused two initial earthquakes on March 17, 2011.
The Ohio well has been shut down and state regulators have worked to reform their injection-well policies.