The 2011 Oklahoma earthquake , the second-largest earthquake in Oklahoma history at magnitude 5.7 , has been linked by some researchers to decades-long injection of brine . A 2015 study concluded that recent earthquakes in central Oklahoma , which includes 5.7 magnitude quake , were triggered by injection of produced water from conventional oil reservoirs in the Hunton Group , and are unrelated to hydraulic fracturing
2011 Oklahoma earthquake
2011 Oklahoma earthquake
Environmental impact of hydraulic fracturing in the United States