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Earthquakes in Central U.S. Tied to Fracking


Over the past few years, the number of earthquakes in the usually seismically calm central United States has skyrocketed. Now scientists are pointing the finger at hydraulic fracturing, better known as “fracking,” as the culprit.

“We’ve been watching the seismicity across most of the country very carefully for a number of years now,” Bill Ellsworth, a seismologist at the U.S. Geological Survey and coauthor of the study, told NPR, “One thing we had begun to notice was there was an unusual number of earthquakes occurring in the middle of the country.”

On average, the central U.S. experienced 21 earthquakes per year between 1970 and 2000. However, the numbers jumped suddenly in 2009, when the area was hit by 50 quakes — and it has been rising every year.

The area was hit by 87 quakes in 2010 and 134 in 2011, according to the U.S. Geological Survey. Officials concluded that the earthquakes are being caused by wastewater from fracking, according to research that will be presented at the Seismological Society of America conference.

Steve Horton, a seismologist at the University of Memphis who has been tracking earthquakes in Arkansas, said there is too strong a link between fracking and earthquakes for it to be a coincidence.

“The earthquakes started after the injection at the two wells started, and they stopped after the injection stopped,” he told NPR.

Geologists aren’t sure exactly how fracking is causing the earthquakes, but say it doesn’t take much to trigger one.

“Small perturbations can tip the scales, allowing an earthquake that might not otherwise happen for a very long time,” Ellsworth said.

Against fracking 01

Against fracking 01 (Photo credit: Bosc d'Anjou)

Hydraulic fracturing is the widening of fractures in a rock layer caused by the high-pressure injection of chemicals with water. Hydraulic fractures form naturally, as in the case of veins or dikes, and industrial fracturing widens or creates fractures to speed up the migration of gas and petroleum from source rocks to reservoir rocks. This process is used to release petroleum, natural gas (including shale gas, tight gas and coal seam gas), or other substances for extraction, via a technique called induced hydraulic fracturing, often shortened to fracking or hydrofracking.

Detractors point to potential environmental impacts, including contamination of ground water, risks to air quality, the migration of gases and hydraulic fracturing chemicals to the surface, surface contamination from spills and flowback and the health effects of these.

A report in the UK concluded that fracking was the likely cause of some small earth tremors that happened during shale gas drilling. In addition, the United States Geological Survey (USGS) reports that, “Earthquakes induced by human activity have been documented in a few locations” in the United States, Japan, and Canada, “the cause [of which] was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies.” The disposal and injection wells referenced are regulated under the Safe Drinking Water Act and   UIC laws and are not wells where hydraulic fracturing is generally performed.

Several earthquakes—including a light, magnitude 4.0 one on New Year’s Eve—that had hit Youngstown, Ohio, throughout 2011 are likely linked to a disposal well for injecting wastewater used in the hydraulic fracturing process, according to seismologists at Columbia University. Consequently, Ohio has since tightened its rules regarding the wells, increased fees, and is considering a moratorium on the practice.
@ wiki


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