Wednesday, October 13, 2010

Second Largest Earthquake in Oklahoma 5.1

The earthquake struck at 9:06 a.m. about six miles east of Norman in Cleveland County, sharply shaking portions of the Oklahoma City metropolitan area. The U.S. Geological Survey estimated the magnitude to be 4.3, but research seismologist Austin Holland said the Oklahoma Geological Survey measured it at 5.1. The higher figure would make Wednesday's temblor the second-strongest here since records began.

The Oklahoma Department of Emergency Management said it had received reports of minor damage, primarily to windows and due to items falling from shelves.

"We had a couple things fall off the wall here at the police department. We all ran outside to see if something hit the station or something like that," Norman police Capt. Leonard Judy said. Only minor damage had been reported through the city, mainly porches cracking or items falling off shelves.

The shaking rattled buildings at the University of Oklahoma in central Norman, sending students, faculty and staff members outside. President David Boren said in a statement that survey teams were dispatched around campus but no structural damage had been found and no injuries were reported.

The first earthquake known to have centered in the State occurred in September 1918. A series of shocks at El Reno produced only minor effects; the strongest was intensity V on September 10. Objects were thrown from shelves. Other shocks occurred on the next day. On December 27, 1929, another tremor centered in the same area was felt in portions of central and western Oklahoma. Some plaster cracked and at least one chimney fell (intensity VI) at El Reno. In addition, clocks stopped, objects moved, and some reports indicated the walls and floors seemed to sway. In several cities, people rushed from their homes in alarm. The total felt area included about 20,000 square kilometers.

The magnitude 5.5 April 9, 1952, earthquake centered near El Reno affected most of Oklahoma and parts of Arkansas, Iowa, Kansas, Missouri, Nebraska, and Texas. Damage from the 10:30 a.m. CST earthquake was not extensive, but many people in the epicentral area were alarmed, some to near panic. Portions of chimneys fell in El Reno and Ponca City (intensity VII). Bricks loosened from a building wall and tile facing of commercial buildings bulged at Oklahoma City. Also, plate glass windows were shattered in the business district of El Reno. The total damage amounted to several thousand dollars. Aftershocks were felt on April 11, 15, and 16, July 16, and August 14; an earthquake that was felt (IV) at Holdenville and Wewoka on October 7 apparently was unrelated to the April 9th event. Homes and buildings shook and some persons were awakened (V) at El Reno from the April 16th shock, which occurred 5 minutes after midnight. Felt reports were also received from Kingfisher, Oklahoma City, Tulsa, and Union City.

Minor damage to a building foundation and plaster (VI) at Concho resulted from two March 17, 1953, earthquakes about an hour apart. The felt area included Calumet, Edmond, El Reno, Minco, Okarche, Peidmont, and Union City.

On February 16, 1956, a shock at Edmont broke windows and cracked plaster (VI). It was also felt strongly at Guthrie, Oklahoma City, and Pawnee. Southeastern Oklahoma was disturbed by an earthquake on April 2, 1956, that produced thundering, rattling, and bumping noises that were heard by many citizens. Buildings shook and objects fell at Antlers, and many persons were alarmed (V). Minor effects were reported from other nearby towns. On October 30, 1956, an area of about 9,500 square kilometers in northeastern Oklahoma was shaken. The maximum intensity of VII was reported west of Catoosa, where a slippage of the formation caused an oil well to be shut down. Minor damage occurred at Beggs and Tulsa; and isolated felt report was received from Electra, Texas.

A broad area (approximately 31,000 square kilometers) of southwestern Oklahoma and the adjacent portion of Texas was affected by an early morning shock on June 17, 1959. Slight damage, consisting of cracks in plaster, pavement, and a house foundation (VI), occurred at Cache, Duncan, and Lawton. Houses were shaken, buildings swayed, and many persons were alarmed. A smaller earthquake on June 15 was felt by many at Ada and nearby places. Dishes were reported broken (V) and a trembling motion was observed.

On January 10, 1961, a mild shock was felt in Latimer and Pittsburgh Counties in southeastern Oklahoma. Thunderous earth sounds were heard in many places (V); no damage was reported. Another earthquake on April 27, 1961, awakened many (V) at Antlers, Coalgate, Hartshorne, Leflore, McCurtain, Panola, Poteau, Talihina, and Wilburton. Once again, thunderous, deep rumbling earth sounds were heard throughout the area.

An October 14, 1968, earthquake caused minor damage at Durant. Walls cracked, and glass in two structures broke (VI). The press reported that a 5 foot tall advertising stand fell over, and canned goods fell from a rack in a supermarket. Slight foreshocks were felt at Durant on October 10 and 11. Intensity IV effects from the October 14 shock were also noted at Caddo.

A magnitude 4.6 earthquake caused some cracked plaster (V) at Wewoka on May 2, 1969. Intensity V effects were reported at several other towns in the region. The total felt area included approximately 33,700 square kilometers in eastern Oklahoma.

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