New 'Big One' forecast: four years

The risk of the southern Kanto region including Tokyo being hit by a major temblor within the next four years could be as high as about 70 percent, according to a study compiled by Monday by a team of researchers at the University of Tokyo's Earthquake Research Institute.

The figure is the same as the 70 percent forecast given for a magnitude 7.0 temblor hitting the region in the ambiguous "next 30 years" that has been repeatedly issued by the government's Headquarters for Earthquake Research Promotion on the basis of intervals between large quakes in the past.

Naoshi Hirata, a professor at the institute and a member of the team, said the risk of a big quake may have risen due to the 9.0-magnitude earthquake that hit in March 2011 off the Tohoku region, spawning tsunami that wiped out wide stretches of the coast.

Since the March disaster, seismic activity has been intensifying in the southern Kanto region and quakes with a magnitude of more than 3.0 have occurred about five times more frequently than in usual years.