Update: This post contained an incorrect characterization of the process of wastewater injection. We’ve updated it to fix the error.
A record number of earthquakes shaking buildings in Oklahoma has both the federal and state government worried that hydraulic fracturing is to blame.
In a rare joint statement, the U.S. Geological Survey and the Oklahoma Geological Survey said this week that injecting wastewater deep into geologic formations in disposal wells is “a likely contributing factor” to increased seismic activity.
“Building owners and government officials should have a special concern for older, unreinforced brick structures, which are vulnerable to serious damage during sufficient shaking,” Bill Leith, the senior science adviser for earthquakes and geologic hazards at USGS, said in the joint statement.
The number of temblors rattling Oklahoma is spiking dramatically. Between 1978 and 1999, Oklahoma experienced an average of just 1.6 earthquakes measuring higher than 3.0 on the Richter Scale per year. In 2013, the state experienced 109 quakes of that magnitude. So far in 2014, just four full months into the year, 145 3.0 tremors have shaken the state.
And the threat of a larger quake is growing: In 2011, a magnitude 5.6 earthquake struck near Prague, a tiny town of about 2,300 residents east of Oklahoma City. “The likelihood of future, damaging earthquakes has increased as a result of the increased number of small and moderate shocks,” the agencies wrote.
The USGS has documented earthquakes caused by drilling activity in recent years in Arkansas, Ohio, Texas and Colorado, all of which have experienced higher numbers of earthquakes after fracking activities increased.
Industry groups are quick to point out there is no definitive link between hydraulic fracturing and increased seismic activity.
“Disposal wells have been used in Oklahoma for more than half a century and have met and even exceeded current disposal volumes during that time. Because crude oil and natural gas is produced in 70 of Oklahoma’s 77 counties, any seismic activity within the state is likely to occur near oil and natural gas activity,” the Oklahoma Independent Petroleum Association told The Oklahoman newspaper in a statement.
Few studies on hydraulic fracturing’s seismic impact have been conducted. A 2012 report by the National Research Council found human activity had been shown to cause just 154 earthquakes in 90 years of monitoring, only 60 of which happened in the United States. Most of those events were caused by conventional oil and gas drilling; just two were directly related to fracking.
The injections of wastewater at high pressure deep into geologic formations, which helps extract the oil or natural gas, changes the pressure underground that keeps the surface from shaking.
In recent years, scientists have found links between human activity and significant seismic events, including the 2011 quake in Prague and a 4.7-magnitude temblor in central Arkansas.
All but seven of Oklahoma’s 77 counties have at least some oil and gas production, making it one of the largest and most lucrative industries in the state.