Wastewater disposal ‘likely factor’ in Oklahoma’s earthquakes
(CNN) — The oil and gas industry’s injection of wastewater deep into the Earth is “a likely contributing factor” to the 50% increase in Oklahoma earthquakes since October, the U.S. Geological Survey said.
The jump in temblors significantly increases the chance for a damaging quake — 5.5 magnitude or greater — in the Great Plains state, the federal agency said.
“As a result of the increased number of small and moderate shocks, the likelihood of future, damaging earthquakes has increased for central and north-central Oklahoma,” the USGS said Monday.
The increase in earthquakes “do not seem to be due to typical, random fluctuations in natural seismicity rates,” a recent USGS statistical analysis found.
Rather, a finding by the USGS and the Oklahoma Geological Survey “indicates that a likely contributing factor to the increase in earthquakes is wastewater disposal by injection into deep geologic formations,” the USGS said.
The Oklahoma Independent Petroleum Association, however, urged a wait-and-see approach in judging the USGS’s assertions.
“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 OIPA and the oil and gas industry as a whole support the continued study of Oklahoma’s increased seismic activity, but a rush to judgment provides no clear understanding of the causes,” the industry group said.
Between last October and April 14, the state experience 183 quakes of magnitude 3.0 or greater, the USGS and Oklahoma Geological Survey said. That is an increase from the state’s long-term average from 1978 to 2008 of only two magnitude 3.0 or larger quakes per year.
“The water injection can increase underground pressures, lubricate faults and cause earthquakes — a process known as injection-induced seismicity,” the USGS said. “Much of this wastewater is a byproduct of oil and gas production and is routinely disposed of by injection into wells specifically designed and approved for this purpose.”
To better gauge the increased quakes, the USGS and Oklahoma officials have added monitoring stations, which now stand at 15 permanent facilities and 17 temporary stations, the agency said.