Asahi Shimbun reported that United States Geological Survey scientists have been investigating the recent increase in the number of magnitude 3 and greater earthquake in the midcontinent of the United States. Beginning in 2001, the average number of earthquakes occurring per year of magnitude 3 or greater increased significantly, culminating in a six-fold increase in 2011 over 20th century levels. A researcher in Center for Earthquake Research and Information of University of Memphis assumes water pushed back into the fault tends to cause earthquake by slippage of fault.Is the Recent Increase in Felt Earthquakes in the Central U.S. Natural or Manmade? United States Geological Survey, 11 April 2012 Over 109 small earthquakes (Mw 0.4–3.9) were detected during January 2011 to February 2012 in the Youngstown, Ohio area, where there were no known earthquakes in the past. These shocks were close to a deep fluid injection well. The 14 month seismicity included six felt earthquakes and culminated with a 3.9 shock on 31 December 2011. Among the 109 shocks, 12 events greater than Mw 1.8 were detected by regional network and accurately relocated, whereas 97 small earthquakes (0.4<<1.8) were detected by the waveform correlation detector. Accurately located earthquakes were along a subsurface fault trending ENE-WSW—consistent with the focal mechanism of the main shock and occurred at depths 3.5–4.0 km in the Precambrian basement. On 19 June 2012, the United States Senate Committee on Energy & Natural Resources held a hearing entitled, "Induced Seismicity Potential in Energy Technologies." Dr. Murray Hitzman, the Charles F. Fogarty Professor of Economic Geology in the Department of Geology and Geological Engineering at the Colorado School of Mines in Golden, CO testified that "About 35,000 hydraulically fractured shale gas wells exist in the United States. Only one case of felt seismicity in the United States has been described in which hydraulic fracturing for shale gas development is suspected, but not confirmed. Globally only one case of felt induced seismicity at Blackpool, England has been confirmed as being caused by hydraulic fracturing for shale gas development." The relative impacts of natural gas and coal Human health impacts A comprehensive review of the public health effects of energy fuel cycles in Europe finds that coal causes 6 to 98 deaths per TWh (average 25 deaths per TWh), compared to natural gas’ 1 to 11 deaths per TWh (average 3 deaths per TWh). These numbers include both accidental deaths and