Accurately simulating movements of a tsunami from occurrence to arrival in urban districts to predict damage
After the Great East Japan Earthquake occurred on March 11, 2011, a massive tsunami caused serious damage to coastal urban districts in eastern Japan. Based on this devastating experience, all disaster-prevention and disaster-reduction measures were reviewed on a nationwide scale in order to prepare for an earthquake and/or tsunami in the future. It is thought that more effective measures can be examined if technology for accurately predicting tsunami damage to urban districts is available.
In fact, in terms of tsunami prediction, Tohoku University and Fujitsu have developed such technology through joint research. Tohoku University has two-dimensional simulation technology, which enables it to predict the expected time of a tsunami’s arrival and its height for a wide range of areas from the sea area where it occurs (wave source) to coastal zones. This technology was actually being used to construct disaster-prevention measures, but it was difficult to simulate the detailed movements of a tsunami in urban districts and coastal areas. On the other hand, Fujitsu has three-dimensional fluid simulation technology developed for purposes such as seawall design, and this technology was thought to accurately simulate the movements of a tsunami rushing toward urban districts because it enables reproduction of a tsunami’s movements against three-dimensional structures such as dykes. However, if it is applied to wide-area simulations covering locations from the wave source to coastal areas, huge amounts of time-consuming calculations will become necessary, so this problem had to be overcome.
The time required for calculation reduced from over 200 years to 160 hours, enabling prediction of damage caused by multiple disasters (earthquake and tsunami)
This recently developed three-dimensional tsunami simulator combines Tohoku University’s two-dimensional simulation technology with Fujitsu’s three-dimensional fluid simulation technology, creating a more accurate reproduction of how a tsunami moves through coastal areas and travels over urban districts or moves along rivers upstream while changing its shape in complicated ways due to landforms and buildings. It also enables more accurate estimation of the damage caused by the impact of a tsunami when it rises violently over breakwaters and falls.
In addition, the new technology substantially reduces the time required to perform simulations. Using the three-dimensional fluid simulator alone, it takes over 200 years to calculate all movements of a tsunami from occurrence to arrival in urban districts, but the three-dimensional tsunami simulator can reproduce tsunami movements in a 10-km2 area— equivalent to the area of a port or bay— in detail after about 160 hours of calculation.
In the years to come, Fujitsu expects the recently developed three-dimensional tsunami simulator to further increase the accuracy of predictions of damage from multiple disasters, which consist of a massive earthquake and tsunami. Fujitsu will contribute to the realization of a disaster-resistant country and cities by proposing use of this three-dimensional tsunami simulator to the national and local governments in Japan.