What Human-Made Earthquakes Mean for Fracking

Critics of fracking raise a myriad of concerns about its environmental repercussions, including methane emissions, water and air pollution. Perhaps no side effect attracts as much opposition to fracking, however, as the earthquakes sometimes set off by the practice or the disposal of related waste. When the U.K. government in November placed a moratorium on new fracking permits, it acted out of concern for associated quakes.

Hydraulic fracturing, as it’s properly known, blasts water, sand and chemicals at high pressure down a well more than a mile underground to crack rocks known as shale so that the oil or gas trapped inside can escape. Fracturing the rocks creates very tiny tremors, but these are imperceptible. The real danger is that if the shale is situated along a geological fault, the fractures can trigger a chain reaction that moves through the rock, causing two blocks of earth to suddenly slip past one another and evoke an earthquake. This is thought to occur more commonly in areas where the underground rocks are already under stress, creating a predisposition for a slip on a fault.