What type of ground motions and tsunamis will strike and how much damage will be caused in the event of the Tokai, Tonankai, and Nankai earthquakes? To develop effective contingency and recovery/reconstruction plans, it is required to predict what would happen in as much detail as possible.

In this project, a number of research institutes worked together to carry out research with a focus on the three themes; search (research and observation), predict (simulation) and be prepared (measures for disaster prevention and damage reduction) and produced the following results.

However, studying the degree of interrelation between earthquakes outside the Nankai Trough and strengthening the liaison with disaster prevention agencies still remain a challenge. It is also necessary to make an effort to improve awareness of and readiness for disaster prevention through education on damage reduction and regional human resource development.

From the aspect of search, we conducted research and observation with state-of-the-art equipment to grasp the current conditions of seismic activities and the Nankai Trough area in as much detail as possible, including crustal structures and interplate coupling around the source region. We placed cutting-edge ocean-bottom seismometers and water-pressure gauges both extensively and densely, integrated the research results obtained on land and on the seabed, and observed natural earthquakes. We also looked into the structure underneath the seafloor by emitting sound waves artificially and tracking how they propagated using a streamer cable floating on the water. This survey started from Hyuga-nada and gradually moved eastward to the Tonankai area and currently to the area off the coast of Suruga Bay.

≫ More information...

From the aspect of predict, we compiled a database of the findings obtained in the research and observation stage, made up a more sophisticated physical model, and established an accurate simulation method that uses a super computer. We have also made research of the sediment from lakes and marshes to understand the diversity of seismic cycles and revealed the history of earthquake occurrence over a period of thousands of years. Based on these, we predicted the type of the next earthquake along the Nankai Trough—whether a single earthquake occurs at a time or more than one simultaneously—and the time lag between the Tonankai and Nankai earthquakes, in the case of a single at a time. The research findings of the project constituted grounds for re-identifying where the west end of the Nankai Trough area is, which is now considered to be the point off the coast of Hyuga-nada.

≫ More information...

Be Prepared (Disaster Prevention and Damage Reduction)

From the aspect of be prepared, we made a highly accurate prediction of strong ground motion and tsunamis and did a detailed simulation of their influence on important urban facilities to draw hazard maps and develop strategies to reduce human suffering. We have also predicted social change, including a decrease in the population of the area due to population outflow and an aging society, which has not been fully considered, and developed more practical recovery/reconstruction plans based on it. We would like to share the results with people on the frontline of disaster prevention and use them to develop more realistic and community-based disaster prevention/damage reduction plans. For this purpose, we regularly hold study meetings in Nagoya, Osaka, Kochi, and other cities.

≫ More information...