2011 Oklahoma earthquake
Chimney damage from the earthquake
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 Oklahoma City
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| Date | November 6, 2011 |
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| Origin time | 03:53:10 UTC |
| Magnitude | 5.7 |
| Depth | 5.2 kilometers (3 mi) |
| Epicenter | 35°35′56″N 96°45′07″W / 35.599°N 96.752°WCoordinates: 35°35′56″N 96°45′07″W / 35.599°N 96.752°W |
| Type | Strike-slip |
| Areas affected | United States |
| Max. intensity | VIII (Severe) |
| Casualties | Two injured |
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Part of the 2009–17 Oklahoma earthquakes |
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The 2011 Oklahoma earthquake was a 5.7 magnitude intraplate earthquake which occurred near Prague, Oklahoma on November 5 at 10:53 p.m. CDT (03:53 UTC November 6) in the U.S. state of Oklahoma. The epicenter of the earthquake was in the vicinity of several active wastewater injection wells. According to the United States Geological Survey (USGS), it was the most powerful earthquake ever recorded in Oklahoma; this record was surpassed by the 2016 Oklahoma earthquake. The previous record was a 5.5 magnitude earthquake that struck near the town of El Reno in 1952. The quake's epicenter was approximately 44 miles (71 km) east-northeast of Oklahoma City, near the town of Sparks and was felt in the neighboring states of Texas, Arkansas, Kansas and Missouri and even as far away as Tennessee and Wisconsin. The quake followed several minor quakes earlier in the day, including a 4.7 magnitude foreshock. The quake had a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale in the area closest to the epicenter. Numerous aftershocks were detected after the main quake, with a few registering at 4.0 magnitude.
In March 28, 2016 the USGS released the USGS National Seismic Hazard Map which concluded that the primary cause of the earthquake in Oklahoma in 2011 was pressure on fault lines from cumulative effects of injecting oil drilling wastewater under high pressure into the underground. Although the 2011 earthquake was the largest on record, the USGS reported that the central and eastern U.S. (CEUS) has undergone the most dramatic increase in seismic activity in the United States since 2009 with an average of 318 earthquakes of magnitude 3.0 a year up from 24 a year from 1973 to 2008. In 2015 there were 1,010 earthquakes in the CEUS region. By mid-March 2016 there were already 226 earthquakes of magnitude 3.0 and larger in the CEUS. "Earthquake rates have recently increased markedly in multiple areas of the Central and Eastern United States (CEUS), especially since 2010, and scientific studies have linked the majority of this increased activity to wastewater injection in deep disposal wells."
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