Fracking has been proven to cause earthquakes, directly and indirectly. The National Research Council settled the debate about indirect cause with a comprehensive study in 2012. The study concluded that the greatest risk of earthquakes does not come from drilling or fracking but from pumping the wastewater from fracking into deep rock reservoirs. Such wastewater injection was blamed for earthquakes that occurred in Youngstown, Ohio, on Christmas Eve and on New Year's Eve 2012, measuring 2.7 and 4.0 on the Richter scale, respectively. The British Columbia Oil and Gas Commission concluded that fracking itself directly caused seismicity in the Horn River shale play, and that those earthquakes damaged underground well structures.