The 37 wastewater disposal wells to be shut down in north-central Oklahoma, where a 5.6 magnitude earthquake struck this weekend, are just a fraction of the state's total number.
There are about 4,200 total wells across the state and about 700 in a 15,000-square-mile "Area of Interest" created by the commission to address earthquakes in the area that includes the epicenter of Saturday's temblor near Pawnee.
The earthquake tied a November 2011 quake as the strongest in recorded state history and was felt as far away as Nebraska, but no major damage was reported.
Not all of the state's wells operate simultaneously, Oklahoma Corporation Commission spokesman Matt Skinner said.
"We estimate that at any one time, there are about 3,200 active disposal wells," Skinner said.
An increase in magnitude 3.0 or greater earthquakes in Oklahoma has been linked to underground disposal of wastewater from oil and natural gas production, and since 2013, the commission has asked wastewater-well owners to reduce disposal volumes in parts of the state where the temblors have been most frequent.
The "area of interest" includes another 211 adjacent square miles that's under the jurisdiction of the Environmental Protection Agency, and Skinner said the commission doesn't know how many wells may be involved there.
Gov. Mary Fallin declared a state of emergency in Pawnee County because of the earthquake. State and local emergency management officials and officials from the U.S. Geological Survey assessed damage