Oklahoma recorded on average not more than 6 earthquakes each year between 1975 and 2008. However, it has now been classified as the second most earthquake-prone region in United States after California.
According to the Independent, scientists have attributed this scenario to the increased oil and gas exploration activity, including hydraulic fracturing or more commonly, fracking.
In 2009 alone, Oklahoma suffered nearly 50 earthquakes. This number surged to at least 1,000 in 2010. However, most of these earthquakes were undetectable to humans-people can only feel earthquakes of magnitude 2.5 and above.
However, Oklahoma’s yearly record of 222 “felt” earthquakes, which was set last year, has already been surpassed in 2014 with 253 tremors felt so far.
“We have had almost as much magnitude 3 and greater already in 2014 than we did for all of 2013… We have already crushed last year’s record for number of earthquakes,” Austin Holland, a seismologist with the Oklahoma Geological Survey told Reuters.
Fortunately, earthquakes are harmless unless they hit a magnitude 4 or higher. On 30 March, a 4.3 magnitude quake shook an area near Oklahoma City. The state also bore the brunt of a 5.6-magnitude earthquake, its largest ever, destroying 14 homes in November 2011.
Scientists have linked the boom in fracking and oil and gas exploration to the increase in the number of tremors in several states. The waste water from oil drilling and fracking is pushed back into the earth to be held in the “injection wells”. Research has shown that such water, when pumped deep underground in the shale rocks can cause seismic activity.
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