In earthquake-prone Japan, 20 seconds could make a difference in minimising loss of life among train passengers who experience traumatic shaking during a major seismic event.The operator of the Shinkansen line between Osaka and Fukuoka in southern Japan is upgrading its earthquake early warning system to give trains operating at speeds of up to 300km/h (186 miles/h) an additional 20 seconds to slow down and avert catastrophe in an area that experts warn could be hit by a megaquake at any...