A sharp rise in the number of earthquakes...over the past few years is almost certainly caused by human activity and could be linked to a boom in shale gas drilling. That is the stark finding of a report by the US government's Geological Survey...Average annual earthquakes rates with a magnitude three or greater jumped from 21 in the three decades before 2000, to...87 in 2010 and 134 in 2011. The scientists now suspect the quakes are caused by wastewater wells, which are a byproduct of oil and natural gas production from...shale...and coal beds...The report is likely to prompt fresh calls for US officials to step up their policing of shale gas operations and to consider stronger regulations to reduce environmental and health risks...However, [US Department of the Interior official David J. Hayes] maintained that the study could not blame hydraulic fracturing for the increased rate of earthquakes.