Damage Characteristic and Field Survey of the 2011 Great East Japan Tsunami in Miyagi Prefecture

Abstract

On March 11th, 2011, the Pacific coast of Japan was hit by a tsunami generated by the largest earthquake (M9.0) in the history of the country and causing a wide range of devastating damage. Using preliminary reported data from many sources, some topics such as tsunami fatality ratio and tsunami fragility curves for structural damage are discussed and compared with other countries. This paper aims to discuss the damage characteristics of this tsunami as well as its mechanism, as observed through field surveys conducted over the 4 months following the tsunami. The field survey covers 13 areas in the Miyagi prefecture from Kesennuma city in the northernmost region to Yamamoto town in the southernmost region. The arrival time of the first tsunami along the coastal areas in the Miyagi prefecture was confirmed by stopped clocks found during the survey. The damage mechanism of coastal structures such as breakwaters, seawalls, tsunami gates, and evacuation buildings was investigated and discussed. Damage characteristics for each area, i.e., urban areas, port, coastal structures, fisheries, and agricultural areas, were also summarized. The conclusions drawn from the data analysis suggest that experience and education (soft countermeasures) are important to reduce the loss of life, as shown for example in the Sanriku area. The field surveys indicate that wood and reinforced-concrete (RC) structures should be balanced to survive both earthquake and tsunami forces, and 1250005-1 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 06/09/15. For personal use only. A. Suppasri et al.the structural design for buildings should be reconsidered after the example in Onagawa town. In addition, coastal structures for tsunami countermeasures (hard countermeasures) should be more properly designed for survival instead of becoming floating debris upon being overturned by a tsunami. The combination of both hard and soft measures is especially necessary for optimizing the outcomes following a great disaster. These recommendations should be taken into consideration in the reconstruction efforts for better tsunami countermeasures in the future.

Performance of coastal sea-defense infrastructure at El Jadida (Morocco) against tsunami threat: lessons learned from the Japanese 11 March 2011 tsunami

“…In this town, the ASCE-EERI team (American Society of Civil Engineering -Subcommittee on Tsunami Loads & Effects) examined areas inside and outside the sea-wall during a posttsunami survey and found a remarkable difference showing more than 90 % of unprotected area destroyed, while only localised damages were observed behind the sea-wall (EERI, 2011). Moreover, the extent of damage was minimal on the lee of the 15.5 m high sea-wall that was overtopped by a 18.1 m wave at Fudai (EERI, 2011;Suppasri et al, 2012). These facts clearly indicate that sea-walls of Japan, even though overtopped, helped mitigating tsunami effects.…”

“…post-tsunami analysis of damage in Japan coastal buildings revealed that trapped air may cause substantial up-lift forces even in RC buildings (Suppasri et al, 2012). Hence, the occurrence of a 1755-like tsunami event could cause massive damages even for RC buildings at El Jadida.…”

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

“…These overturned buildings were built more than 30 years ago over filled soil foundations. A field survey revealed that one of the six overturned buildings in Onagawa was built on a shallow foundation, and the other buildings had a pile foundation; one of the buildings was overturned and moved 70 m from its original position (Suppasri et al, 2012;Latcharote et al, 2014). Based on inundation data, these overturned buildings were fully (or at least nearly) submerged and overturned by the following possible causes: (a) hydrodynamic force, including debris effects; (b) buoyancy force; and (c) weakened foundation associated with soil instability (Yeh et al, 2013).…”

Risk Assessment and Design of Prevention Structures for Enhanced Tsunami Disaster Resilience (RAPSODI)/Euro-Japan Collaboration

“…Existing tsunami vulnerability and risk models are descriptive and limited; some are based on simple empirical relationships between tsunami flow depth and impact metrics such as probability of structural damages or fatalities Suppasri et al, 2012;Dunbar et al, 2011;Berryman, 2005]. Thus, better understanding of the overall vulnerability to tsunamis is necessary to develop efficient mitigation measures against future events.…”