Oklahoma hit by 5.6 magnitude earthquake
One of the strongest earthquakes on record in Oklahoma shook a state where seismic activity became a growing concern and caused tremors that were felt in six neighboring states, the United States Geological Survey.
The earthquake, which struck 14 km northwest of Pawnee in north-central Oklahoma at 7:02 a.m. CDT (1:02 p.m. GMT), had a magnitude of 5.6, corresponding in strength to a earthquake that hit the state in 2011, the USGS reported on its website. No injuries were immediately reported.
The earthquake, which was 6.6 km deep, could offer new ammunition to environmentalists concerned about the side effects of oil and gas production, which has been blamed for a spike in minor to moderate earthquakes in the region.
Pawnee Mayor Brad Sewell said the quake lasted almost a minute, much longer than previous ones which only lasted a second or two.
Part of the facade of an early 20th-century bank building had fallen into a downtown street, he said. The mayor told Reuters he had yet to investigate other parts of the city, which has around 2,200 residents.
“We have had a series of earthquakes over the past few years, but nothing like it,” he said. “It was a long and sustained earthquake.”
Geologists in Oklahoma have documented strong links between increased seismic activity in the state and the injection into the ground of sewage from oil and gas production, according to an agency report. State last year.
Oklahoma records 2 1/2 earthquakes of magnitude 3 or greater daily, a seismicity rate 600 times higher than before 2008, the Oklahoma Geological Survey (OGS) said.
Last year, the state recorded 585 earthquakes of magnitude 3 or greater, up sharply from 109 in 2013. Prior to 2008, Oklahoma averaged less than two a year.
The spike in earthquake activity has placed Oklahoma at the center of a national debate over whether disposal of wastewater from oil and gas production triggers earthquakes. The state economy is heavily dependent on energy production, which represents one in four jobs.
The water in question is extracted from the ground with the oil and gas, separated and reinjected into deep wells.
The drilling technique known as hydraulic fracturing, or “fracking,” generates large amounts of wastewater. But the OGS report says hydraulic fracturing is only responsible for a small percentage of the total volume of wastewater injected into disposal wells.
Zachary Reeves, a seismologist at the USGS National Earthquake Information Center in Golden, Colo., Said the agency had received reports of the Oklahoma earthquake from South Dakota, from Wisconsin, Kansas, Missouri, Arkansas and Texas.
“This is a relatively large earthquake for the region. The central United States does not tend to experience a large number of earthquakes older than five years.”
He said it was the third magnitude 5 earthquake in the state since 2011, and that there had been a dozen or more dozen or more 4 or more in Oklahoma last year.
© Thomson Reuters 2016