Fracking wells in the central and eastern United States have been linked to more than 60% of the earthquakes examined in those regions.
Researchers at the University of Colorado Boulder found that of the underground wells associated with earthquakes, 66% were used for oil recovery, a type of injection well. Other wells, those involving saltwater disposal, were 1.5 times as likely as oil recovery wells to be associated with earthquakes.
They also determined that “high-rate” injection wells were more often associated with earthquakes than wells with lower-rate injection. High-rate wells pump in excess of 300,000 barrels of wastewater into the ground per month. Thousands of injection wells in operation during the past few decades have not appeared to trigger an increase in seismic activity. It is only the more recent, high-rate injection wells that have done so, reported the researchers.
The study, published in Science, said there has been a dramatic increase in the rate of earthquakes in the central and eastern U.S. since 2009, and that earthquakes associated with injection wells have “skyrocketed from a handful per year in the 1970s to more than 650 in 2014,” the university reported.
