U.S. Geological Survey researchers say they're upgrading the strength of an Oklahoma earthquake that struck over the weekend to a 5.8 magnitude, making it the most powerful earthquake ever recorded in the state.
USGS research geophysicist Daniel McNamara said Wednesday the previous strongest recorded quake in Oklahoma — a 5.6-magnitude temblor in 2011 — also is being upgraded to a 5.7-magnitude quake.
Saturday's earthquake centered near the north-central town of Pawnee damaged more than a dozen buildings and left one man with a minor head injury after a fireplace collapsed.
McNamara says the volume of injected wastewater from oil and gas activity likely played a role.
He says Oklahoma's two earthquakes this year greater than magnitude 5.0 will increase the likelihood of larger quakes in the future.