National Public Radio: For the past three decades, Oklahoma averaged about 50 earthquakes a year. But that number has skyrocketed in the past few years. In 2013 - the state's most seismically active year ever - there were almost 3,000.
The quakes are small, and they're concentrated in the central part of the state, where the Erwins live.
Amanda Erwin says that even on a clear day, she knows something's up when the thunder begins: The chandelier swings, and the walls and bed start rumbling. Her husband, Keith, says...