Moderate quake rocks Oklahoma

Minor damage, few injuries reported following mid-Oklahoma earthquake

NORMAN, OK | October 13, 2010

A moderate earthquake shook central Oklahoma Wednesday morning, seismologists and residents said, but no serious damage or casualties have been reported. It was the strongest quake to hit the state in more than 40 years.

The 4.3-magnitude earthquake at 9.06 a.m. CDT was centered approximately 6 miles east of Norman, a city in Cleveland County, or 23 miles southeast of Oklahoma City. It struck about 3.1 miles deep, making it a very shallow earthquake, according to seismologists. According to news reports, the quake was felt throughout the state and northern Texas.

According to Michelann Ooten of the Oklahoma Department of Emergency Management (OEM), minor damage has been reported including broken windows and items falling from shelves. At least two people were treated by emergency responders as a result of a fall.

The United States Geological Survey (USGS) estimated the strength of the earthquake at 4.3 on the Richter scale, while the Oklahoma Geological Survey initially measured it as much stronger 5.1-magnitude earthquake.

The USGS estimated that approximately 99,000 people may have perceived moderate earthquake shaking, which could potentially result in light damage. Up to 2 million others may have felt weak to light shaking.

The Cleveland County sheriff's office reported some minor damage including cans rolling off shelves and a few broken window, but there were no immediate reports of serious damage or casualties. "There is a low likelihood of casualties and damage," the USGS said.

Nevertheless, Jim Bailey, the deputy fire chief in Norman, suggested residents check their homes and businesses for structural damage.

Wednesday's earthquake was unusually strong for the region, which is regularly rattled by minor earthquakes. According to the USGS, most of North America east of the Rocky Mountains has infrequent earthquakes from time to time.

Here and there earthquakes are more numerous, for example in the New Madrid seismic zone centered on southeastern Missouri, in the Charlevoix-Kamouraska seismic zone of eastern Quebec, in New England, in the New York - Philadelphia - Wilmington urban corridor, and elsewhere. However, most of the enormous region from the Rockies to the Atlantic can go years without an earthquake large enough to be felt, and several U.S. states have never reported a damaging earthquake. The earthquakes that do occur strike anywhere at irregular intervals.

Earthquakes east of the Rocky Mountains, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast. A magnitude 4.0 eastern U.S. earthquake typically can be felt at many places as far as 60 miles from where it occurred, and it infrequently causes damage near its source. A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 300 miles from where it occurred, and sometimes causes damage as far away as 25 miles, the USGS said.

This year already marks as a very active year for earthquakes in Oklahoma. According to the Oklahoma Geological Survey, the agency has recorded more than 200 earthquakes in Oklahoma, including nearly 60 which have been felt.

On April 9, 1952, a moderate 5.5-magnitude earthquake struck near El Reno in Oklahoma and caused moderate damage in El Reno, Oklahoma City, and Ponca City. Damage included toppled chimneys and smokestacks, cracked and loosened bricks on buildings, and broken windows and dishes.

One crack in the State Capitol at Oklahoma City was 16 yards long while slight damage was reported from many other towns in Oklahoma and from some towns in Kansas and Texas. The earthquake was caused by slippage along the Nemaha fault and was the largest earthquake ever recorded in Oklahoma. It was felt over most of Oklahoma, Arkansas, Iowa, Kansas, Missouri, Nebraska, and Texas.

The Oklahoma quake wasn't the only one reported in the central U.S. today. A much smaller, 2.7 magnitude earthquake was recorded in Arkansas early Wednesday morning.

(BNO News contributed to this article.)

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