Middle America Is Experiencing a Massive Increase in 3.0+ Earthquakes

"A new United States Geological Survey study has found that middle America between Alabama and Montana is experiencing an 'unprecedented' and 'almost certainly man-made' increase in earthquakes of 3.0 magnitude or greater. In 2011, there were 134 events of that size. That's six times more than were normally seen during the 20th century.
In some regions, the increase in earthquakes is even greater than six fold. For example, in Oklahoma over the past half-century, there were an average of 1.2 quakes of greater than 3.0 magnitude per year. Since 2009, there have been more than 25 per year."
"A naturally-occurring rate change of this magnitude is unprecedented outside of volcanic settings or in the absence of a main shock, of which there were neither in this region,"  scientists wrote in the study.  (source: The Atlantic)