2016-11-18. Fracking can prime faults for subsequent quakes.

posted Nov 20, 2016, 5:26 PM by Alan Gould
By Ian Randall, Science. For GSS Energy Flow chapter 2 and Energy Use chapter 3. Excerpt: Hydraulic fracturing in western Canada can prime faults for earthquakes that strike months after fracking ceases, reports a new study published this week in Science. Although it has long been known that the injection of wastewater into disposal wells can trigger earthquakes by increasing pore pressure and destabilizing fault lines, rarely has fracking itself been identified as the source of tremors. ...Looking at seismic records near Fox Creek, in northwest Alberta, where there are six drilling sites, researchers found an intermittent set of induced earthquakes between December 2014 and March 2015, clustered around fracking operations. The majority of seismicity occurred during fracking as the elastic response of the rock caused mounting stress. However the largest quake, which had a magnitude of 3.9, struck on 23 January 2015—2 weeks after fracking had been completed. ...In the future, they say, drillers should take account of such risks, especially when they fail to recover fracking fluids....  http://www.sciencemag.org/news/2016/11/fracking-can-prime-faults-subsequent-quakes