US researchers say oil and gas production may explain a sharp increase in earthquakes in the Midwestern region of the country, from Alabama to the Northern Rockies.
A US Geological Survey team reported that the rate of earthquakes had jumped six-fold from the late 20th century through last year, and the changes were "almost certainly man-made," according to the Associated Press.
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However, while the researchers suggested some kind of link to oil and gas production, it was not clear why the two might be related.
“It remains to be determined how they are related to either changes in extraction methodologies or the rate of oil and gas production," Russia Today quoted the abstract for USGS study, published by the Seismological Society of America, as saying.
However, Digital Journal wrote, the researchers offered a possible explanation, saying that drilling required the disposal of millions of gallons of waste water for each well, and that the number of wells had increased dramatically over the past 10 years.
Previous work has linked earthquakes to injecting huge amounts of wastewater deep into the earth.
A recent series of earthquakes in north-eastern Ohio, most recently on New Year's Eve, prompted that state's Department of Natural Resources to suspend development by natural gas drillers of five deep wastewater disposal wells.
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And Arkansas imposed a permanent moratorium on disposal wells due to enhanced seismic activity near the Fayetteville Shale, RT reported.
"The acceleration in activity that began in 2009 appears to involve a combination of source regions of oil and gas production, including the Guy, Arkansas, region, and in central and southern Oklahoma. Horton, et al. (2012) provided strong evidence linking the Guy, AK, activity to deep waste water injection wells," RT cited the study saying.
Their study also linked a relatively mild increase in quake activity starting in 2001 to a methane production area along the state line between Colorado and New Mexico, the AP reported.
Since 2009, more quakes had been seen in a variety of oil and gas production areas, including some in Arkansas and Oklahoma, the researchers said.
The study is scheduled to be presented at a scientific meeting later this month States.
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