Monday, April 13, 2015

Fracking's unintended consequence: Oklahoma quakes

In a piece published today in The New Yorker titled Weather Underground: The Arrival of Man-Made Earthquakes, Rivka Galchen writes: 

"Until 2008, Oklahoma experienced an average of one to two earthquakes of 3.0 magnitude or greater each year. (Magnitude-3.0 earthquakes tend to be felt, while smaller earthquakes may be noticed only by scientific equipment or by people close to the epicenter.) In 2009, there were twenty. The next year, there were forty-two. In 2014, there were five hundred and eighty-five, nearly triple the rate of California. Including smaller earthquakes in the count, there were more than five thousand. This year, there has been an average of two earthquakes a day of magnitude 3.0 or greater.
"William Ellsworth, a research geologist at the United States Geological Survey, told me, “We can say with virtual certainty that the increased seismicity in Oklahoma has to do with recent changes in the way that oil and gas are being produced.” Many of the larger earthquakes are caused by disposal wells, where the billions of barrels of brackish water brought up by drilling for oil and gas are pumped back into the ground. (Hydraulic fracturing, or fracking—in which chemically treated water is injected into the earth to fracture rocks in order to access oil and gas reserves—causes smaller earthquakes, almost always less than 3.0.) Disposal wells trigger earthquakes when they are dug too deep, near or into basement rock, or when the wells impinge on a fault line. Ellsworth said, “Scientifically, it’s really quite clear.”

Read the full story here

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