The earthquake that shook Kansas and four other states Wednesday was one of the strongest ever recorded in Oklahoma.
The earthquake struck at 9:06 a.m. about six miles east of Norman. At least two people sustained minor injuries. Minor damage — primarily to windows and from items falling — was reported.
"You definitely would have felt it in Wichita," said Don Blakeman, a geophysicist with the U.S. Geological Survey's earthquake information center in Golden, Colo.
Tremors in Wichita lasted for about a minute.
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The Geological Survey initially rated the quake at 4.5 magnitude but later dropped it to a 4.3. Research seismologist Austin Holland said the Oklahoma Geological Survey measured it at 5.1. The higher figure would make it the state's second-strongest quake on record.
Blakeman said the quake was felt up to 170 miles away in parts of Kansas, Arkansas, Missouri and Texas.
Oklahoma Gov. Brad Henry said teams have been dispatched to assess the earthquake's impact on state infrastructure.
Henry said in a statement that crews from the Oklahoma Department of Transportation are checking roads and bridges, and the Department of Central Services and the Department of Public Safety are reviewing state facilities and buildings for damage. He says no significant problems had been reported.
Don Steeples, who teaches earthquake seismology at the University of Kansas, said the energy impact of a 4.3 quake is equivalent to about a half million pounds of exploding dynamite.
"My guess is the earth in Wichita probably moved up and down less than a tenth of an inch," he said.
An earthquake occurs when rock slips on either side of a fault.
"That causes a vibration that goes until it dies out," Steeples said. "A tremor just means something shakes."
He said he wasn't sure how much of Kansas felt the tremors, but said he had confirmed reports from as far away as Emporia.
Kansas historically has not been a prime player in the world of earthquakes.
"It's relatively benign," Steeples said of the state. "Nothing like California but also more active than places like North Dakota."
Kansas typically sees about a dozen earthquakes with a 2.0 magnitude each year, he said.
"We get a 4.0 every couple of decades or so, and a 5.0 every century," Steeples said.
Kansas' last significant earthquake occurred in June 1989, when a 4.0 was registered at the epicenter about 20 miles northwest of Hays, he said.
Over the past year or two, there have been a series of earthquakes in Jones and Spencer, Okla., which are near Norman.
A magnitude-5.5 earthquake struck El Reno, just west of Oklahoma City, in 1952. Another struck in northeastern Indian Territory in 1882, according to the U.S. Geological Survey. The Oklahoma Geological Survey rated that quake at 5.0.