Researchers say oil and gas production may explain a sharp increase in the number of earthquakes from Alabama to the Northern Rockies. A U.S. Geological Survey team reports that the rate of quakes jumped six-fold from the late 20th century through last year, and that the changes were "almost certainly man-made."
A recent series of earthquakes in northeastern 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 wastewater disposal wells. And Arkansas recently imposed a moratorium on disposal wells because of increased seismic activity near the Fayetteville Shale.
But another expert was not convinced of a link to oil and gas operations. Austin Holland, an Oklahoma state seismologist, said the new work presents an "interesting hypothesis" but that the increase in earthquake rates could simply be the result of natural processes. Holland said clusters of quakes can occur naturally,and that scientists do not yet fully understand the natural cycles of seismic activity in the central United States. Comprehensive earthquake records for the region go back only a few decades, he said, while natural cycles stretch for tens of thousands of years.