2009–16 Oklahoma earthquake swarms
Seismicity map for Oklahoma and nearby areas – Blue circles indicate earthquakes from pre-2009 while circles of other colors indicate earthquakes since 2009.
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| Date | 2009–present |
|---|---|
| Duration | About eight years |
| Type | Intraplate earthquakes |
| Areas affected | Central and North-Central Oklahoma South-Central Kansas Dallas–Fort Worth metroplex |
| Total damage | Unknown |
| Max. intensity | VIII (Severe) (November 5, 2011 Oklahoma earthquake) |
| Casualties | Minor injuries associated with November 5, 2011 Oklahoma earthquake, 1 injured in September 3, 2016 Oklahoma earthquake |
| Greatest magnitude |
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| Mean depth | 5.43 km (3.37 mi) in 2014 |
| Total events | >2,550 in OK since January 1, 2009 (USGS) ≥157 in KS since January 1, 2013 (USGS) 31 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 fewer than two 3.0+ magnitude earthquakes per year since 1978 to hundreds per year in 2014, 2015, and 2016. 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 wastewater produced during oil extraction that has been injected more deeply into the ground.
Two of the most significant earthquakes in these swarms were the November 5, 2011 Prague earthquake east of the Oklahoma City area and the September 3, 2016 earthquake near Pawnee, north of Prague. The 2011 Prague earthquake, at reported magnitude 5.6, was at the time the strongest recorded earthquake in the history of Oklahoma. The 2016 earthquake was initially reported to be an identical 5.6 magnitude, but this was later upgraded to 5.8, making it the strongest earthquake on record. Simultaneously, the USGS upgraded the magnitude of the Prague earthquake to 5.7. Numerous seismologists had advised local residents of an even greater risk of earthquakes in 2014, by which time the number of earthquakes had increased to a dangerously high level. In response to the major increase in earthquakes in the Central United States, the United States Geological Survey (USGS) began developing a new seismic hazard model to account for risk associated with induced seismicity. By June 26, 2014, no fewer than six individual earthquake sequences in Oklahoma had been identified and named by the Oklahoma Geological Survey (OGS). Other swarms have been observed in south-central Kansas and North Texas.
In March 2013, a peer-reviewed paper published by a research team led by seismologist Katie Keranen at the University of Oklahoma in the scientific journal Geology reported that "the volume of fluid injected into the subsurface related to the production of unconventional resources continues to rise" and that there was a link between the "zone of injection and the seismicity" potentially triggering the Prague earthquake. On 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 until that time, the USGS reported that the central and eastern U.S. (CEUS) had 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.
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