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

Abstract

Abstract-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, nonstructural (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.

Possible Failure Mechanism of Buildings Overturned during the 2011 Great East Japan Tsunami in the Town of Onagawa

“…However, there was sufficient time for water to flow inside the buildings because of the long-period wave. Thus, only the accumulated air between the top of the windows and the ceiling generated buoyancy force (Suppasri et al, 2013). The survey team also stated that most of the piles were probably pulled out and broken at the pile head as a result of ground shaking, hydrodynamic force, buoyancy force, and soil liquefaction.…”

Modelling of tsunami-induced bore and structure interaction

“…The structure's dimensions and the pressure loads after being scaled are then used in the FE model. These types of structures were chosen as the focus of the FE modelling because they are fairly typical of the coastal buildings widely damaged by the tsunamis of 2004 and 2011 (Como and Mahmoud, 2013;Suppasri et al, 2013). The dimensions and material properties of the representative timber structure's members in the FE model follow the provisions set out in the International Residential Code (ICC, 2009).…”

“…By far, the majority of structures damaged or destroyed in these events were residential buildings. After the 2011 East Japan tsunami, Suppasri et al (2013) stated that 115 163 houses were heavily damaged, 162 015 houses were moderately damaged and 559 321 houses were partially damaged. Many of those houses were constructed from timber.…”

Introduction to “Historical and Recent Catastrophic Tsunamis in the World: Volume I. The 2011 Tohoku Tsunami”

“…For comparison, the dataset collected by international research teams following the 2004 Indian Ocean tsunami, which affected more than 14 countries around the Indian Ocean, contains approximately 1,000 points in the NOAA/WDC tsunami database at http:// www.ngdc.noaa.gov/hazard/tsu_db.shtml. SUPPASRI et al (2013) investigated the effects of the 2011 Tohoku tsunami on coastal defence structures and different building types in Japan. Although the Japanese coasts were well protected by tsunami countermeasures, such as sea walls or flood gates, they were often either insufficient to prevent significant overtopping or were damaged badly themselves by the tsunami.…”