Small earthquakes at fracking sites may indicate bigger tremors to come

Tiny tremors caused by hydraulic fracturing of natural gas near the surface could be early signs of stressful conditions deep underground that could destabilize faults and trigger larger earthquakes. Stanford geoscientists have devised a way of detecting thousands of faint, previously missed earthquakes triggered by hydraulic fracturing, or "fracking." A drill rig at the Fayetteville Shale gas play in Arkansas. The area was shaken by earthquakes in 2010 and 2011 following injections of wastewater from natural gas operations into deep underground wells. (Image credit: Bill Cunningham/USGS) The technique can be used to monitor seismic activities at fracking operations to help reduce the likelihood of bigger, potentially damaging earthquakes from occurring, according to the new study. "These small earthquakes may act like canaries in a coalmine," said study co-author William Ellsworth , a professor (research) of geophysics at Stanford's School of Earth, Energy & Environmental Sciences. "When they happen, they should be viewed as cautionary indicators of underground conditions that could lead to larger earthquakes." Fracking involves injecting high-pressure fluid underground to crack open rocks and release the natural gas trapped inside. As the rocks crack, they produce tiny earthquakes that were typically too small to be detected - until now.