A U.S. Geological Survey USGS team has found that a sharp jump in earthquakes in America’s heartland appears to be linked to oil and natural gas drilling operations.As hydraulic fracturing has exploded onto the scene, it has increasingly been connected to earthquakes. Some quakes may be caused by the original fracking — that is, by injecting a fluid mixture into the earth to release natural gas or oil. More appear to be caused by reinjecting the resulting brine deep underground.Last August, a USGS report [PDF] examined a cluster of earthquakes in Oklahoma and reported:

via Shale shocked: USGS links ‘remarkable increase’ in earthquakes to fracking | Grist.