70% chance that a Magnitude 7 or greater quake could hit Tokyo region in the next four years: research

New research by the University of Tokyo’s Earthquake Research Institute suggests a 70% chance that a Magnitude-7 or greater earthquake could hit the Tokyo region sometime over the next four years.
This new research, widely reported in the media, considerably steps up the timetable that such an event might happen in the future. The Earthquake Research Committee of Japan estimates a 70% chance that a Magnitude 7 or greater earthquake could hit the greater Tokyo urban region sometime over the next 30 years.
In contrast, the Earthquake Research Institute suggests a 98% chance that a Magnitude 7 or greater earthquake will hit the Kanto region, encompassing Tokyo and Yokohama, sometime over the next 30 years.
“A [Magnitude] 7 or greater (M 7+) earthquake in this region at present has high potential to produce devastating loss of life and property with even greater global economic repercussions,” the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area says in a posting on the Institute’s website. “The Central Disaster Management Council of Japan estimates the next great earthquake will cause 11,000 fatalities and 112 trillion yen (US$1 trillion) economic loss.”
In contrast to the assumptions on which the Japanese government’s estimate is based, the Institute’s research factors in a recent increase in moderate seismic activity in the area.
“The group at the university’s earthquake research institute said the number of moderate quakes in the capital region measuring magnitude three or bigger surged to 343 in the six-month period after the [Magnitude 9] March [2011 Tokohu] quake, up from 47 in the previous six months,” the Press Association reported. “Based on a theory that the probability of bigger earthquakes rises in proportion to an increase in smaller quakes, the team calculated a 98% likelihood of a magnitude 6.7 to 7.2 earthquake striking Tokyo over the next 30 years.”
“When we ask when a probability of such a quake reaches 70%, then we get a 70% chance over the next four years,” the Press Association quotes seismologist Shinichi Sakai, a team researcher, as saying.