 Underscoring the risks facing Japan, a 2012 research institute investigation has "determined there is a 70% chance of a magnitude-7 earthquake striking the Tokyo metropolitan area within the next four years, and 98% over 30 years".The March 2011 earthquake was a magnitude-9.Between 2005 and 2007, three Japanese nuclear power plants were shaken by earthquakes that far exceeded the maximum peak ground acceleration used in their design.