Although the key to the mechanism of the earthquake is said to be the behavior of the crust plate, and have been found in recent years is the location where a plurality of plates each other Semegi hit just below Tokyo Bay.And very, very near future, large earthquake of M7 class that there epicenter is he that attack in the Tokyo metropolitan area.* “There is a plate boundary collide in Tokyo Bay area” ─ Hirata direct professor of the University of Tokyo Earthquake Research Institute of so told in the briefing with Governor Shintaro Ishihara.Recently, it’s researchers probability that the Tokyo metropolitan area epicentral large earthquake occurs within four years have become a hot topic to announce that it 70%. Hirata professor is also the Principal Investigator of the sub-project of “metropolitan area Earthquake Disaster Mitigation special project” of the Ministry of Education, detailed for the plate structure just below the capital. Metropolitan area directly under the two continental plates (the Eurasian Plate, North American Plate) under the Pacific Ocean plate from the east is, is subducting Philippine Sea plate from the south. And established a seismograph of 400 locations in the metropolitan area in the project.The plate structure I revealed.He As a result, it was found that area plate boundary each other Semegi directly under Tokyo Bay. In addition, the report of Professor Hirata “close to the figure of the earthquake that hit the Tokyo metropolitan area”, there is a description of a similar earthquake directly under Tokyo Bay that happened on the history.According to it in the Tokyo metropolitan area, has repeatedly occurred large earthquake of M7 class between the M8 class massive earthquake with a period of 200 to 400 years.One, in the ancient documents that was a big earthquake that occurred in 1812 “Sekiguchi diary”, Yokohama, houses collapsed in Kawasaki, a large number of dead is depicted how out.Region, which is estimated from the ancient documents of description it was a seismic intensity 6 Yokohama, Shinagawa from Kawasaki, spread in Setagaya, seismic intensity 5 north Soka, Saitama Prefecture, west Atsugi, Kanagawa Prefecture, Fujisawa, south 及 up in Kanazawa-ku, Yokohama he has Nde. Tokyo Bay direct type of earthquake that occurred is imminent is, it is unclear whether similar manner.However, when an earthquake takes into account the tendency to occur with a periodicity, it It will not be definitely be quite helpful to predict the size and damage. Professor Hirata et al earthquake six months ago, the earthquake occurrences of M3~6 class that have occurred in the metropolitan area within six months after the earthquake investigation.Made a “probability evaluation method aftershock” by combining a statistical method.And he probability of large earthquakes of M7 class occurs in the metropolitan area was flipping a shocking figure of 70 percent over the next four years. Says Akihiro specific researcher Takeuchi of Tokai Earthquake Prediction Research Center.The reason for earthquake occurs frequently in “Kanto There are several.One is that there is a place where it remained divided by the Great East Japan Earthquake.And for earthquake shock was too large, and the force applied to the rock varies, it is unstable.Future, a major earthquake that hit the Kanto region there are three.Metropolitan area just below, Boso, is Tokai earthquake.Should be under the Kanto Plain there are active fault of undiscovered.There is also a possibility that the epicenter, as soon as possible investigation is needed “We he had built a huge metropolis on top of the nest of earthquake.