In the event of large-scale disasters such as Nankai Trough mega earthquake and earthquake directly under Tokyo Metropolitan area, it is required to secure necessary trunk line cargo transportation soon after an earthquake and to quickly secure the requisite minimum transportation of key emergency supplies for recovery and reconstruction. In addition, the interaction of earthquakes, tsunamis, and high waves with the ground might cause coastal disasters, so it is necessary to reduce such risks. Therefore, this research aims to establish techniques for predicting seismic motions and damage to structures caused by the strongest, long-duration earthquakes. Furthermore, the research will develop new techniques for reinforcing existing structures for improving their anti-seismic capacity, assessing damage during on-site damage surveys, and implementing emergency measures. In addition, the research elucidates the phenomenon of tsunami caused by submarine landslides, soil performance against the effects of tsunami, high waves, and flows, and method of countermeasures.

In order to predict waveform and damage in the largest earthquakes, we observed strong ground motions in ports and airports and organized and analyzed their data, investigated earthquake disasters and their causal factors, and worked on the development of novel methods for predicting near-source strong ground motions and liquefaction-induced ground subsidence and flow.As for the development of a method for predicting near-source strong ground motions, we have made progress in developing and examining a source model that is capable of considering not only strong seismic motions that are caused by the rupture of deep asperities on the faults but also the effects of faults shallow slip. Concerning our activity on a system that enables swift and proper determination of the availability judgement of mooring facilities following earthquakes in an effort to improve surveys of earthquake damage and its causal factors, our team has been discussing with the MLIT and its Regional Development Bureaus how to utilize the system and also conducted experiments to test the system on site.

Concerning our activity involving damage-reduction technology against the largest earthquakes, we examined ways to predict the deformation that may occur in coastal facilities due to seismic motions and proceeded with developing a technology to allow coastal facilities to exhibit their performance at an early stage.

Concerning the interaction of earthquakes, tsunamis, and high waves with ground dynamics, our team proceeded with activities to develop techniques for evaluating the stability of coastal structures against sucking out, sinking, and other adverse phenomena, thus leading to effective countermeasures, and also to develop methods for evaluating the deformation and failure characteristics of coastal geotechnical structures in relation to waves and flows, and for reinforcing the structures against them. In terms of effective novel countermeasures to better protect against sucking out and sinking, the team proceeded working on sucking out prevention method involving filter layers and caisson joint transmission wave reduction method that were proposed in the previous year, by considering a wider range of soil conditions, external forces, and structural conditions and examining the applicability to various conditions. In FY 2021, the filter-layer-based sucking out prevention method was implemented on the seawall for protecting the new runway at Naha Airport, while the caisson-joint transmission wave reduction method was implemented at Yokohama Port. In addition, both of these methods were included in the partial revision of the Technical Standards and Commentaries for Ports and Harbors (April 1, 2022).