CUSHING, Okla., Nov. 7 (UPI) -- There have been no reports of pipeline problems stemming from an earthquake in Oklahoma near the main U.S. oil storage hub in Cushing, a state agency said.
Six seismic events were recorded in Oklahoma by the U.S. Geological Survey over the last 24 hours and one was recorded just over the state border in Kansas. The largest quake to strike the area was a magnitude-5.0 event in Cushing, Okla., which was followed an hour later by a smaller magnitude-2.3 tremor.
The Oil and Gas Division of the Oklahoma Corporation Commission said it was working to assess the status of the energy infrastructure tied to Cushing in the wake of the quake.
"The OCC's Pipeline Safety Department has been in contact with pipeline operators in the Cushing oil storage terminal under state jurisdiction and there have been no immediate reports of any problems," the commission said in a statement.
Unconfirmed reports suggest some operators had shut down infrastructure as a precaution, but so far there are no verified accounts of damage to pipelines in the area.
According to the Oklahoma Geological Survey, the area around Cushing has been an active zone for seismic events since 2015.
The outbreak comes less than five days after a similar string of quakes struck about 8 miles southwest of Pawnee, Okla. The strongest there was a magnitude-4.5 quake.
The Oklahoma Corporation Commission issued a directive after the Pawnee events that limited the amount of work associated with wastewater disposal wells in the area. According to the commission, wastewater injected into the so-called Arbuckle formation near Pawnee "poses the largest potential risk for earthquakes in Oklahoma."
One of the U.S. states with a significant amount of shale oil and natural gas, a study from the USGS found the disposal of oil and gas-related wastewater is the "primary reason" for an increase in seismic activity in central states like Oklahoma. That process is different from hydraulic fracturing.
Pawnee is about 25 miles north of Cushing.