Oklahoma typically had about 50 earthquakes a year until 2009. Then the number spiked, and 1,047 quakes shook the state last year, prompting researchers to install seismographs in the area.
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Oklahoma's largest quake in decades buckles highway; rattles resident
Central Oklahoma continued to experience dozens of aftershocks Sunday, nearly 24 hours since the state's strongest earthquake since 1952 was felt throughout the region.More than ten aftershocks measuring at east 3.0 magnitude were reported Sunday, in the hours after a 5.6-magnitude earthquake took residents by surprise Saturday night. The temblor rattled homes and structures, causing belongings to scatter in houses and sending strident, booming sounds through the area.
Kathy Crawson, a nurse with a community hospital in Prague, Oklahoma, about six miles from the quake's epicenter, said Sunday the experience was terrifying, but she was getting used to the aftershocks.
"We have felt several aftershocks. I just felt one a few minutes ago," said Crawson.
The 5.6-magnitude quake struck four miles east of Sparks in Lincoln County at 11:53 p.m. ET Saturday.
It hit struck the same area where a 4.7-magnitude quake struck just hours earlier -- at 3:12 a.m. ET Saturday.
By 8 a.m. Sunday, geologists had recorded more than 30 aftershocks.
The strongest quake previously reported was of magnitude 5.5 on April 9, 1952, according to the Oklahoma Geological Survey.
According to The Oklahoman newspaper, the weekend's tremors were reportedly felt as far away as Illinois, Kansas, Arkansas, Tennessee and Texas.
Some 200 miles away from the epicenter, in Garland, Texas, resident Noel Kennedy said he felt the quake.
Austin Holland, a seismologist with the state geological survey, said he spent all day gathering new data from seismological instruments.
"We have experienced over 10 aftershocks above 3.0," said Holland.
The quakes happened near the location of a 4.7-magnitude quake last year near the Wilzetta fault, also known as the Seminole uplift, Holland said.
"Being from Oklahoma, I had never experienced anything since last year. It's a wild, strange feeling. You can actually see it, the walls, the floors, the noise. I was scared," nurse Crawson, of Prague, said Sunday.
While last year's quake indicated there was new seismic activity in the area, Holland said he was surprised by "the 5.6."
According to the OGS website, the frequency of earthquakes has temporarily increased in Oklahoma but are not inconsistent with normal seismicity in the region.
In 2010, the OGS recorded 1,047 earthquakes in Oklahoma -- most of them small temblors, but 103 were reported felt, the agency said..
http://articles.cnn.com/2011-11-06/us/us_oklahoma-earthquake_1_47-magnitude-quake-largest-quake-56-magnitude-quake?_s=PM:US
