There are plenty of reasons to worry about fracking—groundwater contamination, methane leaks, that flaming tapwater thing. But can it really cause earthquakes? That's the question the US Geological Survey set out to answer after a spate of tremors in the Midwest—an area not usually known for earthquakes—alerted scientists to the possibility that some of them might be manmade.
Seismic activity in the Midwest started increasing around twelve years ago but picked up significantly in the past few years, says seismologist Bill Ellsworth, the lead author of a new USGS study examining potential links between fracking and earthquakes in the region. Since 1970, the baseline for earthquakes in the Midwest measuring above a 3.0 hovered at around 21 per year, but beginning in 2001, that number began to rise.