OKLAHOMA CITY, Feb. 18 (UPI) -- Oklahoma's recent spate of earthquakes have been more frequent and stronger than typical, a state quake expert says.
More than 25 of the temblors felt in the last two months had magnitudes of 3 or higher, KOCO-TV, Oklahoma City, reported Tuesday.
That's an unusually large number, said Michael Lewchuk, an earthquake expert at the Casady School in Oklahoma City.
"We typically have somewhere between 50-100 in one full year," he said.
More than 150 earthquakes have been recorded in Oklahoma in the past week, the Oklahoma Geological Survey says.
The U.S. Geological Survey says the state typically receives no more than three earthquakes a year of 3-magnitude or greater. In recent years, the average number of significant quakes has jumped to 40 a year.
A dozen of the strongest quakes in the past week were centered just off Interstate 35 near Guthrie. About half of them were recorded in a 24-hour period ending Monday morning.
Lewchuk said the earthquakes could not be specifically linked to drilling or waste water injection, but added, "it's counter intuitive to think there's not some relation."
Chesapeake Energy, an Oklahoma City-based firm, is being sued by 28 Arkansas homeowners for allegedly causing earthquakes. They claim Chesapeake's injection wells have caused thousands of quakes that have damaged their homes.