Lessons Learned from the 2011 Great East Japan Tsunami: Performance of Tsunami Countermeasures, Coastal Buildings, and Tsunami Evacuation in Japan

In 2011, Japan was hit by a tsunami that was generated by the greatest earthquake in its history. The first tsunami warning was announced 3 min after the earthquake, as is normal, but failed to estimate the actual tsunami height. Most of the structural countermeasures were not designed for the huge tsunami that was generated by the magnitude M = 9.0 earthquake; as a result, many were destroyed and did not stop the tsunami. These structures included breakwaters, seawalls, water gates, and control forests. In this paper we discuss the performance of these countermeasures, and the mechanisms by which they were damaged; we also discuss damage to residential houses, commercial and public buildings, and evacuation buildings. Some topics regarding tsunami awareness and mitigation are discussed. The failures of structural defenses are a reminder that structural (hard) measures alone were not sufficient to protect people and buildings from a major disaster such as this. These defenses might be able to reduce the impact but should be designed so that they can survive even if the tsunami flows over them. Coastal residents should also understand the function and limit of the hard measures. For this purpose, non-structural (soft) measures, for example experience and awareness, are very important for promoting rapid evacuation in the event of a tsunami. An adequate communication system for tsunami warning messages and more evacuation shelters with evacuation routes in good condition might support a safe evacuation process. The combination of both hard and soft measures is very important for reducing the loss caused by a major tsunami. This tsunami has taught us that natural disasters can occur repeatedly and that their scale is sometimes larger than expected

A Study on Influential Factors on Building Damage in Kesennuma, Japan from the 2011 Great East Japan Tsunami

A number of buildings were damaged by the 2011 Great East Japan tsunami in the Tohoku area. The research objective is to determine the significant predictor variables of the level of building damage. This paper used detailed data on damaged buildings in Kesennuma City, Japan, collected by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). The tested explanatory parameters included the inundation depth, number of floors, volume of the building, debris flow, structural material, and function of the building. Through multinomial logistic regression, the results found that the number of floors was significantly associated with the damage level; the inundation depth, structural material (reinforced concrete and masonry), and function of the building (commercial facility, transportation/storage facility, and public facility) were partially associated with the damage level. This study can contribute to academic research by assessing the contribution of different variables to observed damage data by applying statistical analysis, as well as the practical contribution of providing an examination of the predominant factors driving tsunami damage to buildings