Expert Sound Alarm: Tokyo at Risk of Devastation from Imminent Earthquake Directly Beneath the Tokyo Metropolitan Area

Disturbing tremors have been occurring frequently.

During the week of March 2-9, there were 79 earthquakes of intensity 1 or higher in various parts of Japan. The most active area is Chiba Prefecture, where more than 40 tremors of intensity 1 or higher have occurred since late February, with epicenters in the southern and eastern offshore areas. Yoshinobu Tsuji, a former associate professor at the Earthquake Research Institute of the University of Tokyo and a visiting researcher at the Fukada Geological Research Institute. 

The fact that there have been so many earthquakes in a row suggests that something big is going on underground. This is a different situation from before. It could be a sign of a huge earthquake.

Slow slip, in which plates and faults slide slowly, is thought to be the cause of the Chiba earthquake. What is frightening is that the current situation is very similar to the situation just before a huge earthquake occurred in the past. Even before the Great East Japan Earthquake in March 2011 and the Noto Peninsula Earthquake in January this year, slow-slip earthquakes had occurred frequently. Robert Geller, a professor emeritus at the University of Tokyo and a seismologist, points this out.

The mechanism of earthquake occurrence is complex and cannot be predicted by current science. A major earthquake could occur anywhere at any time. However, statistics have shown that the probability of a major earthquake occurring in the vicinity of a seismic swarm is somewhat higher.

According to the GSI, the slow slip in Chiba caused the plate boundary to move southeastward by 2 cm. The greatest concern is an earthquake directly under the Tokyo metropolitan area.

If the epicenter moves further southeast, be careful. It will stimulate the triple junction of the Sagami Trough, the Japan Trench, and the Izu-Ogasawara Trench, which can cause an earthquake directly under the capital.