Japan Researchers to Study Strains Off Iwate Prefecture to Help Predict Risk of Huge Quakes

Yomiuri Shimbun file photo
A survivor of the Great East Japan Earthquake and subsequent tsunami is rescued by a Maritime Self-Defense Forces helicopter in Rikuzen-Takata, Iwate Prefecture, on March 12, 2011.
The Yomiuri Shimbun

To help predict the risk of powerful earthquakes more accurately, a team of researchers from Tohoku University and the Japan Agency for Marine-Earth Science and Technology will soon begin intensive observations of crustal movements.

Their work will be based on the assumption that strain, which can generate energy for a massive earthquake, may have accumulated in the seabed north of the epicenter of the Great East Japan Earthquake that occurred in 2011. There is precedent for a huge earthquake being followed by another after a certain period of time in an adjacent marine area, and the team will examine the movement of the seabed to assess the risk.

According to the team, the observations are to be conducted along the Japan Trench off the coast of Iwate Prefecture. A fault in the seabed is said not to have slipped during the 2011 earthquake.

The team will use the Wave Glider, an autonomous unmanned surface vehicle powered by wave and solar energy. The vehicle will obtain information from six observation points on the seabed and deliver it to land via satellite.

The team will begin operating this new system in April and conduct intensive observations two or three times annually for several years. This will allow the movement of the seabed to be ascertained in detail, in a bid to detect unusual phenomena that could be a precursor to a huge earthquake.

This method would cost less than one-tenth of conventional means. In the past, researchers had to go offshore by ship, costing several tens of millions of yen each time. Observations were limited to about once a year.

Tohoku University Prof. Ryota Hino said, “I want to collect basic data for areas that we have not observed at all, and make this the first step in predicting the next great earthquake that will cause a huge tsunami.”

It is understood that major earthquakes tend to occur in neighboring areas. For example, two powerful earthquakes occurred within several tens of hours to several years later in areas along the Nankai Trough off the Pacific coast of central to southwestern Japan, where massive earthquakes are said to occur repeatedly.

About three months after the magnitude-9.1 earthquake off Sumatra, Indonesia, in 2004, which killed and left many people missing, another earthquake measuring 8.6 on the Richter scale struck waters to the south.