Update: November 5,2011
40 miles away from Norman, near Prague, a sudden earthquake swarm has developed in Lincoln County Oklahoma.
Magnitudes 4.7, 3.4, 2.7, 2.7, 3.3, 3.3, 3.4, and they’re still coming…

The earthquakes are clearly occurring on a known fault as observed on a map from the Leonard Geophysical Observatory

( “The largest earthquake ever recorded in the state of Oklahoma struck Saturday night. The quake had a magnitude of 5.6, and its epicenter was four miles east of Sparks in Lincoln County, according to the Oklahoma Geological Survey. The quake hit at 10:53 p.m.”

The quake was the result of movement along the Seminole Uplift Structure, a broad subsurface feature, which is approximately 50 miles wide and over 75 miles long. The feature itself has a number of anticlines and faulted noses that account for much of the historic, prolific oil production in that area.


Original Post:
A magnitude 4.3 shook up residents around Norman Oklahoma during the morning of 13-Oct-2010, while the number of higher magnitude 2010 earthquakes continue to rise well above averages.

There is currently some discrepancy regarding the magnitude of the event. The USGS quickly rated a 4.3, IRIS has it rated 4.5, while the Oklahoma Geological Survey rated a magnitude 5.1

The Norman earthquake in Oklahoma, originating 5 miles underneath Lake Thunderbird, was one of the strongest ever felt in the state. The strongest was a magnitude 5.5 located in El Reno during 9-Apr-1952 when chimneys fell and plate glass windows were shattered.

Earthquakes in Oklahoma are not rare with between 50 and 150 recorded each year. However this year during 2010, more than 200 have rattled the state, while at the same time people around the world have been sensing a higher number of earthquakes.

The Oklahoma Geological Survey, Leonard Geophysical Observatory, verifies the 2010 earthquake increase in the following statement.

2010 has been an active year for earthquakes in Oklahoma.  The OGS has recorded more than 200 earthquakes which occurred in Oklahoma.  There have been nearly 60 earthquakes which were felt.  This is a much greater number than in years past (see figure below).  The seismicity at this point appears consistent with normal background seismicity.  Presently, the number of Earthquakes recorded in Oklahoma for 2010, appear more numerous than in years past but the fact remains that earthquake monitoring in our state was only initiated 50 years ago.   This is a very short period of the Earth’s history, and this activity may not be as unusual as it appears to us today.


Interestingly just two days prior to the Norman earthquake, 290 miles due East, a magnitude 4.0 followed by numerous aftershocks rattled central Arkansas, a location within the New Madrid seismic zone.

Residents of Oklahoma may soon be joining the ranks of Californians for Earthquake Insurance


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