"I guess my ladder wasn't set very solid, and it just shook me off of it," Tankersley said by phone.
Randy Keller, director at the Oklahoma Geological Survey, said the quake "came in loud and strong on all of our seismic stations."
Norman police Capt. Tom Easley said there were no known reports of injuries or damage in the city, but residents flooded the 911 lines.
Rick Smith, warning coordination meteorologist for the National Weather Service, Norman Forecast Office, was in his office at the National Weather Center in Norman.
"It was a rumble. It didn't last long, but there was a jolt at the end," Smith said.
At the University of Oklahoma, a section of glass in the ceiling at Dale Hall was shattered, though it remained in place, and there was no immediate confirmation it was caused by the earthquake.
In Purcell, about 12 miles south of Norman, the sensation was intense, said Erica Lippel, a spokeswoman for the Purcell Police Department.
"Everybody pretty much went out in the street," she said.
A bumpy 2010
There have been about 570 earthquakes in the state this year, many too small to be felt. A 4.1 magnitude quake was reported on Feb. 27 near Sparks along the Turner Turnpike northeast of Oklahoma City.
The cause of Wednesday's quake and other recent ones could result from a buried fault or even oil and gas drilling activity, said Estella Atekwana, professor of hydrogeology at Oklahoma State University. The exact cause wasn't determined.
A 5.5 magnitude earthquake on April 9, 1952, is the largest ever recorded in Oklahoma, according to the U.S. Geological Survey. That one at El Reno, Oklahoma City and Ponca City cost thousands of dollars.
Earthquakes that wouldn't be felt in places like California, where subsurface conditions are different, can be felt here, Randy Keller, the Oklahoma Geological Survey director said in 2009. The hard rock beneath the Sooner State is better at conducting the seismic waves.Recap: Oklahoma earthquake chat Previous Oklahoma earthquake coverage Blog: Earthquake history in Oklahoma Oklahoma earthquake: Report what you felt Oklahoma earthquake: View the "shake map" USGS: Magnitude 5.1
Staff Writers Michael Kimball, Matt Patterson, Robert Medley, James Tyree, David Zizzo, Rick M. Green, Kathryn McNutt, Jane Glenn Cannon.