2009–16 Oklahoma earthquake swarms

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Oklahoma area earthquake swarms
Map of earthquakes greater than 3.0 magnitude
Seismicity map for Oklahoma and nearby areas – Dark blue circles indicate earthquakes from pre-2009 while circles of other colors indicate earthquakes since 2009.
Date 2009–present
Duration About fifteen 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
Greatest magnitude
Mean depth 5.43 km (3.37 mi) in 2014[1][lower-alpha 1]
Total events >7,140 in OK since January 1, 2009 (USGS)[2]
>2,079 in OK since June 9, 2008 (OGS)[3][lower-alpha 2]
≥2,360 in KS since January 1, 2013 (USGS)[4]
≥195 in N TX since January 1, 2009 (USGS)[5][lower-alpha 3]

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.[6] Scientific studies attribute the rise in earthquakes to the disposal of salt water produced during oil extraction that has been injected more deeply into the ground.[7][8]

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.[9] Multiple seismologists advised local residents of an even greater risk of earthquakes in 2014 when the number 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.[10] Other swarms have been observed in south-central Kansas and North Texas.

According to data from the United States Geological Survey, there have been approximately 2,068 earthquakes in Oklahoma with moment magnitudes greater than or equal to 3.0,[11] about 65 earthquakes with magnitudes greater than or equal to 4.0, and two earthquakes with magnitudes greater than 5.0 associated with the earthquake swarms from the beginning of 2009 through May 29, 2016.[12]

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 November 5, 2011 Prague earthquake.[13][14] 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.[13][15][16] 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.[16] The oil industry pressured the OGS to release a statement saying "The interpretation that best fits current data is that the Prague earthquake sequence was the result of natural causes" which they later recanted.[17]

Background

The first earthquake known to have occurred within the boundaries of Oklahoma occurred in September 1918 when a series of shocks was 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 20,000 km2 (7,700 sq mi).[18]

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 15 meters (49 ft) 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.[18][19]

Scattered earthquakes occurred in Oklahoma between 1952 and 1969 with intensities as high as VII.[18] Between 1978 and 2008, the average long-term rate of earthquakes was approximately two earthquakes of magnitude 3.0 or greater per year.[6] However, in 2009, this number jumped to 20 with the beginning of several swarms of earthquakes in Oklahoma.[20] Research suggests that most of the significant earthquakes in Oklahoma since the 1930s may have been induced by oil production activities.[21]

Earthquakes

2011–12

Damage from the magnitude 5.6 earthquake on November 5, 2011, the largest earthquake on record in the state

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Main article: 2011 Oklahoma earthquake

A rise in seismicity in Oklahoma was observed in 2011. Early on the morning of November 5, 2011, an earthquake with a magnitude of 4.8 struck an area east of Oklahoma City roughly centered between Sparks and Prague. At the time, it was the strongest earthquake associated with the rise in Oklahoma's seismicity. Less than a day later at 10:53 p.m., a 5.6 Mw earthquake occurred near the location of the preceding 4.8 magnitude earthquake, becoming the strongest earthquake observed with any of the swarms as well as the strongest earthquake in the history of Oklahoma. This also resulted in the reclassification of the magnitude 4.8 earthquake as a foreshock and the 5.6 magnitude earthquake as the mainshock.[22] The earthquake received over 66,000 "Did You Feel It?" responses nationwide sent to the United States Geological Survey.[23] It was believed that the earthquake had occurred along the Wilzetta Fault, also known as the Seminole Uplift. Following this earthquake, several portable seismograph stations were established by the USGS, OGS, and University of Oklahoma School of Geology and Geophysics to aid with detection of future earthquakes in the area.[9] The 5.6 Mw mainshock was followed by a magnitude 4.8 aftershock slightly under two days later, and numerous other aftershocks occurred in the following months.[24][25] Through the end of 2011, 64 earthquakes were recorded, nearly double the number recorded for 2010.[20]

2012 saw a decrease in seismic activity in Oklahoma when compared to 2011, with a recorded annual total of 35 earthquakes magnitude 3.0 or greater, 29 less than recorded in the previous year.[20]

2013–14

On December 7, 2013, an earthquake occurred within the city limits of Oklahoma City in an area south of Lake Arcadia with a magnitude of 4.5 Mw. This was the strongest earthquake to occur in Oklahoma since the November 5, 2011 earthquake near the Prague–Sparks area east of Oklahoma City.[26] For 2013, an estimated 109 earthquakes occurred according to the Oklahoma Geological Survey, a number substantially higher than in any previous year going back to 1978.[20]

The 2014 total of 3.0+ magnitude earthquakes by May 2 was higher than the entire yearly total for 2013, at over 140 earthquakes. The number of earthquakes in Oklahoma increased by about 50% from October 2013 to May 2, 2014, prompting the United States Geological Survey to issue an uncommon "Earthquake Advisory" for Central Oklahoma warning of the elevated possibility of damaging, 5.5+ magnitude earthquakes. This was the first advisory in the United States ever issued east of the Rocky Mountains and remains effective.[6]

File:Oklahoma seismic hazard map.jpg
Seismic hazard map for Oklahoma for 2014 – this hazard map does not account for the recent earthquakes and potentially induced seismicity

On July 17, 2014, the United States Geological Survey released an updated map identifying seismic hazard for the continental United States.[27] However, the earthquakes occurring in much of Oklahoma were not included in the creation of the map, for it is believed by the USGS that some degree of the earthquakes may have been induced by wastewater injection, and the map is meant to represent natural seismicity alone due to the unpredictable nature of earthquakes created by human industrial activities. Austin Holland of the OGS voiced concerns about the removal of the earthquakes in the map's creation, and he said "By removing them, we are underestimating the potential of serious seismic hazard in Oklahoma." William Ellsworth of the USGS responded by mentioning that the USGS was working on a new hazard model; "Everyone here thinks quakes, regardless of origin, need to be accounted for in our hazard model," he said.[28]

The swarms, while initially located primarily further south, traveled northward from Central Oklahoma into Logan County in early 2014. Additional earthquake swarms initiated in north-central Oklahoma, including areas near Medford, Oklahoma. The latter swarms crossed into southern Kansas in 2013. Many earthquakes have also occurred in the southernmost part of Kansas since they began, with the most significant being a magnitude 4.9 earthquake on November 12, 2014, the strongest earthquake produced by the swarms since a magnitude 4.5 earthquake struck in Northeast Oklahoma City on December 7, 2013 almost a year earlier.[26][29]

2015–16

File:Oklahoma 3.0 earthquake bar graph since 1978.png
Graph of 3.0+ magnitude earthquakes on the moment magnitude scale known to have occurred annually in Oklahoma through February 17, 2016 – a drastic increase can be seen starting in about 2009. Click to enlarge.
File:Oklahoma seismicity animation.ogv
Animation of all M3+ earthquakes in Oklahoma from January 2, 2008 to April 3, 2016
File:Induced earthquakes in Oklahoma area.png
Zones of suspected induced seismicity in the Oklahoma area

By the end of 2014, 567 earthquakes of at least magnitude 3.0 were recorded in Oklahoma, more than the number of 3.0+ magnitude earthquakes from the previous 30 years combined.[30] In 2014, there were over twice as many earthquakes recorded in Oklahoma as in California, making Oklahoma the most seismically active state in the contiguous United States by a substantial margin. A review by EnergyWire examined earthquakes of greater than or equal to magnitude 3.0, and found that seismic activity in Oklahoma had been spreading northward into Kansas, which experienced a major jump in earthquakes from 2013 to 2014.[31] As in southern Kansas, earthquakes increased in frequency in North Texas, with over 130 earthquakes occurring there from 2009 to early 2015.[32]

For the first time, the United States Geological Survey would include earthquakes believed to have connections to industrial activities in its National Seismic Hazard Map which sets standards for construction and insurance rates.[33] According to USGS National Seismic Hazard Project head Mark Petersen, an updated version of the map will become available before the end of 2015. This marks a deviation from the past, with the USGS updating the National Seismic Hazard Map annually instead of every six years.[34]

The United States Geological Survey updated its National Seismic Hazard Map in 2014; however, potentially induced earthquakes were intentionally not considered in this analysis as geologists were uncertain how to incorporate non-tectonic earthquakes. Several months later in April 2015, a comprehensive assessment was released analyzing the link between the increase in seismic activity in the Central United States and oil and gas operations. Seventeen induced seismicity zones for earthquakes over the past 50 years were delineated in this assessment, including one region encompassing northern Oklahoma and parts of southern Kansas, a second region covering central Oklahoma down to the Oklahoma–Texas border, and a third region encompassing the Dallas–Fort Worth area of Texas.[35][36]

On April 21, 2015, the Oklahoma Geological Survey abandoned its skepticism of the possible link between earthquakes and industrial activities and said in official statement that it "considers it very likely that the majority of recent earthquakes, particularly those in central and north-central Oklahoma, are triggered by the injection of produced water in disposal wells." In 2013, the seismicity rate was "70 times greater than the background seismicity rate observed in Oklahoma prior to 2008", potentially although unlikely explainable by natural variations in seismicity, but the seismicity rate by the time of the statement was "about 600 times greater than the background seismicity rate" and was "very unlikely the result of a natural process."[37][38][39]

Late on August 16, the number of earthquakes in Oklahoma with moment magnitudes of ≥3.0 for the year of 2015 surpassed the yearly total for 2014 of 585 such earthquakes with over six times as many MW 3.0+ earthquakes as California. Through August 19, Oklahoma average 2.5 MW 3.0+ earthquakes a day in 2015; if earthquakes were to continue to occur at this rate through the remainder of 2015, Oklahoma would total over 912 such earthquakes, an increase of over 55% as compared to 2014.[40]

On December 29, a magnitude 4.3 earthquake struck in northeastern Oklahoma County near the town of Edmond. The quake caused structural damage to at least one home and caused power outages to over four thousand residents.[41] This was followed by a 4.2 magnitude earthquake on the morning of January 1, 2016, again in northeastern Oklahoma County in a nearby area.[42] Then on January 6, two earthquakes - one of magnitude 4.4 and one of magnitude 4.8 - struck near Fairview in northwest Oklahoma within just 30 seconds of each other. On February 13, slightly over five weeks later, an earthquake with an estimated magnitude of 5.1 struck 28 kilometers (17 miles) northwest of Fairview.[43] It was the third-strongest earthquake ever recorded in Oklahoma.[44]

Cause

Cumulative number of earthquakes in the central and eastern U.S. Most of the increase (shown in red) is due to induced seismicity in Oklahoma and nearby Kansas.[45]

Researchers have correlated the increase in earthquakes in central and north-central Oklahoma to injection disposal of produced water from two actively drilled stratigraphic intervals: the Mississippi Lime play, in north-central Oklahoma and extending into Kansas, which uses hydraulic fracturing; and the Hunton dewatering play, in central Oklahoma, which does not use hydraulic fracturing.[46] Both Mississippi Lime and Hunton plays produce large volumes of produced water; frac flowback makes up less than 5 percent of the injected wastewater.[47] More than 70 percent of the produced water from both plays is disposed through permitted Class II injection wells into the Arbuckle Group where it rests on Precambrian basement. The increase in pore pressure can release pre-existing stresses along faults in the basement rock.[48]

Between 2011 and 2014, the percentage of earthquakes spatiotemporally associated with injection wells has increased sharply by 87%.[49] A study of historic earthquakes has concluded that "much of the earthquake activity in the 1950s and 1980–1990s was induced" by injection of wastewater in deep disposal wells and the cluster of activity since 2009 is not consistent with the natural rate of fluctuations seen in the past.[50]

Governmental response

In September 2014, in response to the swarms of earthquakes, Oklahoma Governor Mary Fallin announced the creation of a "Coordinating Council on Seismic Activity" to help promote further understanding of the increase in seismicity. Fallin added, "We believe that by linking scientists and energy experts, we can develop sound regulatory practices and policies in our state while also alleviating any questions our citizens might have." The council, led by Michael Teague, is expected to include input from multiple areas, including "the Oklahoma Geologic Survey, the Oklahoma Corporation Commission, the Oklahoma Energy Resources Board, the University of Oklahoma, Oklahoma State University, the Oklahoma Independent Petroleum Association, the Oklahoma Oil and Gas Association, and various state legislators".[51] However, some criticized the council, saying it included too many representatives from the oil and gas industry; additional critics pointed out the fact that Michael Teague was the Oklahoma Secretary of Energy. Teague replied by saying that he was also concerned with environment, and he followed by adding, "We are talking to environmental groups and industry folks and academic folks and state agencies and how do you bring them all together?"[52]

After EnergyWire obtained Oklahoma Geological Survey email correspondence through an Oklahoma Open Records Act request in 2015, it was found that after the OGS acknowledged a link between oil and gas operations and the ongoing earthquakes in the latter part of 2013, state seismologist Austin Holland was called into a meeting with University of Oklahoma President David L. Boren and oil executives. Holland had previously spoken with a senior official of the United States Geological Survey discussing the connection between a swarm of earthquakes near and east of Oklahoma City. Holland wrote to USGS science advisor Bill Leith in 2013 "Since early 2010 we have recognized the potential for the Jones earthquake swarm to be due to the Hunton dewatering," but he followed by saying "But until we can demonstrate that scientifically or not we were not going to discuss that publicly." In October 2013, a joint statement between the OGS and the USGS announced that "activities such as wastewater disposal" may be a "contributing factor to the increase in earthquakes." Holland was requested a week later to come to Oklahoma Corporation Commission headquarters by then-Commissioner Patrice Douglas for a meeting. Also sent for was then-president of exploration at Continental Resources, Jack Stark. As Holland recounted in a later email, Stark and Douglas were "concerned" by the joint statement.[17] This precedes the Oklahoma Geological Survey's April 2015 change in position where the agency acknowledged that the earthquakes were "very unlikely the result of a natural process."[37]

In April 2015, after the Oklahoma Geological Survey acknowledged that the tremendous increase in the frequency of earthquake occurrence is likely due to the injection of produced water in disposal wells,[37] the State of Oklahoma launched a website providing information about earthquakes in the state, including an interactive map where both earthquakes and disposal wells can be plotted.[38][39]

"Traffic light" system

The Oklahoma Geological Survey has developed a "traffic light" system, which assigns "yellow light" status to some disposal wells, imposing limits on injection rates and pressures, and "red light" status to some injection wells, requiring them to shut down.[53] Injection wells are regulated by the Oklahoma Corporation Commission, which regulates oil and gas in the state. The Corporation Commission has also required more than 50 disposal wells drilled down to the basement to be plugged back.

Following earthquake activity in Alfalfa County, Oklahoma near the Kansas–Oklahoma border in late-January 2015, the Oklahoma Corporation Commission ordered SandRidge Energy to shut down an injection well it was operating. This was the second wastewater injection well directed to "shut in" or halt operations by the agency since a new monitoring system was established in 2013. According to Matt Skinner, a spokesman from the commission, the directive was issued on February 3 in response to a magnitude 4.1 earthquake recorded in the area four days earlier. According to Skinner, "They were operating under a 'yellow light' permit with language that said shut in if there's any seismic activity."[54]

Potential damage

File:USGS damage forecast for earthquakes in the Central and Eastern U.S. in 2016.png
250px

As a result of the magnitude 5.6 earthquake on November 5, 2011, an estimated one million dollars in damage occurred in and around the Prague area.[55] So far, there has not been a significant amount of damage reported from other earthquakes, but in April 2014, the United States Geological Survey released an analysis indicating that "the likelihood of future, damaging earthquakes [in central and north-central Oklahoma] has increased as a result of the increased number of small and moderate shocks."[6]

In light of the greatly increased earthquake activity, about 15% of Oklahomans had purchased earthquake insurance by early 2015 according to Oklahoma Insurance Commissioner John D. Doak.[56]

On June 30, 2015, the Oklahoma Supreme Court ruled that homeowners who had suffered injuries or property damage as a result of frequent earthquakes believed to be caused by industrial activities could legally sue for damages in trial courts. This ruling was issued in spite of efforts by the industry to prevent such lawsuits from being accepted. The case, originally brought before a state court by Sandra Ladra, who had sustained injuries during the 2011 Oklahoma earthquake, named the Spess Oil Company and New Dominion, two oil and gas companies, as defendants in the case. The case was initially dismissed by a state court under the premise that such cases must go before the Oklahoma Corporation Commission as required by state law. After Ladra's lawyer appealed to state supreme court, the 7-to-0 ruling on June 30 was made.[57]

See also

Notes

  1. ↑ This mean depth figure is for Oklahoma only.
  2. ↑ Earthquakes included in this total have a minimum magnitude of 3.0. The total from the United States Geological Survey is significantly higher than that from the Oklahoma Geological Survey as the OGS total deliberately neglects to include earthquakes with magnitudes 3.0. Information from the OGS is still included as its dataset is not identical to that of the USGS. This data is valid through April 3, 2016.
  3. ↑ Seismic activity ceased in North Texas in early February 2016.[5]

References

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  8. ↑ Fracking-Linked Earthquakes May Strike Far from Wells, Live Science, Becky Oskin, May 2, 2014. Retrieved 19 January 2016.
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  46. ↑ David Brown, "Dispelling myths about seismicity," AAPG Explorer, Oct. 2015.
  47. ↑ "Oklahoma earthquakes linked to oil and gas drilling," AAAS, 18 June 2015.
  48. ↑ K. M. Keranen and others, [1] Science, .
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External links

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