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}} years | maxmagnitude = 5.6 (Mw) (November 5, 2011 Oklahoma earthquake near Sparks/Prague area) | meandepth = in 2014 | type = Intraplate earthquakes | affected = Central and North-Central Oklahoma South-Central Kansas Dallas–Fort Worth metroplex | damage = Unknown | intensity = VIII (''Severe'') (November 5, 2011 Oklahoma earthquake) | casualties = Minor injuries associated with November 5, 2011 Oklahoma earthquake | events = ≥5,270 in OK since January 1, 2009 (USGS)>8,400 in OK since January 2, 2008 (OGS)≥2,120 in KS since January 1, 2013 (USGS)≥184 in N TX since January 1, 2009 (USGS) }} Beginning in 2009, the frequency of earthquakes in the U.S. State of Oklahoma rapidly increased from an average of less than two 3.0+ Mw earthquakes per year to hundreds in 2014 and 2015. Thousands of earthquakes have occurred in Oklahoma and surrounding areas in southern Kansas and North Texas since 2009. Scientific studies attribute the rise in earthquakes to the disposal of salt water produced during oil extraction that has been injected into the ground. One of the most significant earthquakes of this swarm was a 5.6 magnitude earthquake east of the Oklahoma City area which was the strongest earthquake in the history of Oklahoma. Multiple seismologists advised local residents of an even greater risk of earthquakes in 2014 when the amount of earthquakes increased to a dangerously high level. In response to the major increase in earthquakes in the Central United States, the United States Geological Survey began developing a new seismic hazard model to account for risk associated with induced seismicity. To date, no fewer than six individual earthquake sequences in Oklahoma have been identified and named by the Oklahoma Geological Survey. Other swarms exist in south-central Kansas and North Texas. According to data from the United States Geological Survey, there have been approximately 1,553 earthquakes in Oklahoma of greater than or equal to moment magnitude 3.0 and about 47 earthquakes with moment magnitudes greater than or equal to 4.0 associated with the earthquake swarms from the beginning of 2009 through November 3, 2015. ==Background== The first earthquake known to have occurred within the boundaries of Oklahoma occurred in September 1918 when a series of shocks were felt in El Reno, Oklahoma, the strongest of which was an estimated intensity V on September 10. On September 27, 1929, another tremor of intensity VI was centered in the same area and was felt in central and western Oklahoma; minor damage occurred in nearby areas and one chimney fell. The total affected area was approximately . A magnitude 5.5 earthquake occurred near El Reno on April 9, 1952 at 10:29 a.m. CST (16:29 UTC), and at the time, it was the strongest earthquake ever recorded in Oklahoma. Most of Oklahoma was affected, as were parts of Arkansas, Iowa, Kansas, Missouri, Nebraska, and Texas. Damage was not extensive, but local residents were alarmed, and several thousands of dollars in damages occurred. Chimneys were toppled, walls were cracked, windows were broken, and bricks were loosened from buildings. In Oklahoma City, a crack measuring was found in the State Capitol following the earthquake. The earthquake, which occurred along the Nemaha Fault, had a maximum intensity of VII near the epicenter.〔 Scattered earthquakes occurred in Oklahoma between 1952 and 1969 with intensities as high as VII.〔 Between 1978 and 2008, the average long-term rate of earthquakes was approximately two earthquakes of magnitude 3.0 or greater per year.〔 However, in 2009, this number jumped to 20 with the beginning of several swarms of earthquakes in Oklahoma. Research suggests that most of the significant earthquakes in Oklahoma since the 1930s may have been induced by oil production activities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2009–15 Oklahoma earthquake swarms」の詳細全文を読む スポンサード リンク
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