Magnitude 5.6 earthquake in Oklahoma ties biggest area has seen

Likely example of recent earthquakes induced by disposal well injections. 

Scott K. Johnson
USGS map showing the epicenter of Saturday's earthquake (star) and contours of estimated shaking intensity.
Oklahoma has suddenly become a seismic state over the last decade, as an abundance of small earthquakes has accompanied the expanded use of deep injection wells. The wells are used to dispose of wastewater that would be expensive and difficult to treat. Instead, it gets pumped into salty aquifers that are already unsuitable sources of drinking water. Most of the wastewater comes from oil and gas wells in the region—some of which involve fracking, but many of which are older, “conventional” wells.
Fluid pressure in the saline aquifers seems to be transmitting into the underlying igneous and metamorphic basement rock, where it “lubricate” ancient faults and allow them to move.
At about 7:00 am Saturday morning (local time), things moved again: a magnitude 5.6 earthquake struck near Pawnee, Oklahoma, northeast of Oklahoma City. Unless the magnitude estimate changes after further analysis, this will tie the strongest earthquake the region has seen during this strange period—a magnitude 5.6 near Prague in 2011. In February of this year, Fairview, Oklahoma experienced a 5.1.
At least one injury was reported in Pawnee, according to the Tulsa World. A handful of buildings saw some damage, including an historic downtown building that lost some of the sandstone blocks from the veneer on its exterior wall, which fell to the sidewalk. A local grocery store saw lots of stock end up on the floor and damage to its suspended ceiling.
The Oklahoma Corporation Commission, which regulates the disposal wells in the state, responded by ordering a precautionary shutdown of 37 wells in a 700 square mile area around Pawnee over the coming week and a half. Oklahoma has been working to get a handle on ways to limit injections and thereby reduce the risks of earthquakes.
This is certainly nothing like a magnitude 7 earthquake in heavily populated coastal California, but it’s significant for a state still getting used to the possibility of seismic activity—a state where buildings and infrastructure have not been designed with seismic activity in mind. Analysis is necessary to link this specific earthquake to disposal well activity, but it fits with the recent trend in the region that researchers believe clearly points to earthquakes being induced by injections.
Magnitude 5.6 earthquake in Oklahoma ties biggest area has seen Reviewed by Bizpodia on 18:36 Rating: 5

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