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Press Release Detail

Sunday, October 23, 2016  15:03

Issued: Friday, April 20, 2012  00:00

Lessons Learned from Japan Tsunami

Tsunami exacuation:Lessons from the Great East Japan earthquake and tsunami of March 11th 2011
S. Fraser, I. Matsuo, G.S. Leonard, H. Murakami
GNS Science Report 2012/17  April 2012
The Great East Japan moment magnitude (Mw) 9.0 earthquake occurred at 14:46 (Japanese Standard Time) on March 11th 2011. Significant seabed displacement generated the subsequent tsunami, which caused significant damage in Iwate, Miyagi, Fukushima and Ibaraki Prefectures. As a result of this event over 19,000 people are dead or missing, with over 295,000 collapsed buildings along 600 km of affected coastline.
Reconnaissance-level analysis of evacuation preparedness and actions related to the tsunami has been carried out using semi-structured interviews with local disaster prevention officials and emergency services officials. Interviews were carried out in Tarō Town, Kamaishi City, Ōfunato City (Iwate Prefecture) and Kesennuma City, Minami-Sanriku Town, Ishinomaki City and Natori City (Miyagi Prefecture). The interviews covered tsunami awareness, observations and response to natural and informal warnings; style and derivation of evacuation maps; official warning timing and dynamics; evacuation timing, mechanisms
and issues; and vertical evacuation buildings – availability, designation, public awareness, utilisation, relationship to maps, and post-event review. The report also presents examples of hazard and evacuation maps and signs employed in the Tōhoku region.
Experiences in Tōhoku during this event are relevant to tsunami mitigation activities in the State of Washington and in New Zealand, which co-funded this research. These areas have local earthquake and tsunami risk posed by the Cascadia Subduction Zone and the offshore Hikurangi subduction margin, respectively. This report provides recommendations for further development of tsunami mitigation activities in these areas, based on findings from the interviews.
Overall there was a 96% survival rate of those living in the inundated area of the
municipalities visited. This can be attributed to mostly effective education and evacuation procedures. Schools education, hazard maps and exercises appear to be the most commonforms of education. Community involvement in planning of evacuation maps, routes and buildings is common, with many places conducting regular community-level exercises.
Hazard and evacuation maps lacked consistency and both maps and safe locations were generally designed for a tsunami height that under-represented the worst case scenario.
The natural warning of long ground shaking (reported as more than two minutes, and often more than three) was widely agreed as enough by itself to have triggered evacuation. Sea walls reduced effective observation of the natural warning of unusual ocean behaviour in many places, and fostered a false sense of security in some locations.
Although an early warning system is often seen publicly as key infrastructure in enhancing tsunami resilience, the expectation of official warnings (and their content) may have slowed the time taken for people to initiate evacuation in Tōhoku, compared to if there had been total reliance on natural warnings. Exposure to previous false ‘major tsunami’ warnings apparently led to complacency in this event, despite this earthquake feeling much larger than anything previously experienced. The philosophy of tsunami tendenkowas shown to be a positive education tool which promoted immediate self-evacuation and save many lives.
Peoples’ movements during and after evacuation reveal that many people died unnecessarily due to delayed evacuation or non-evacuation as a result of social or parental responsibility, lack of education or scepticism of warnings. Widespread use of motor vehicles caused traffic congestion in some areas, when walking, running or cycling would have been much more effective and saved lives.
Many people returned to the evacuation zone too early in some places because they had not seen the wave arrive at the expected time given in official warnings, or because they expected no more waves to arrive. It is critical that people have the awareness that the first wave may come later than estimated by rapid scientific analysis, and the largest wave may not be the first.
The evacuation strategy in place at March 11th 2011 was appropriate in that it sent people to safe locations, used maps and community involvement and was regularly exercised in many places. Some evacuation centres were not located far enough inland or on high enough ground because they were not designated using the worst-case tsunami inundation.
There was extensive effective use of both designated and informal vertical evacuation buildings. The most important considerations for effective use are sufficient height (in relation to expected inundation depth), reinforced concrete construction, community engagement, owner agreement, signage, 24-hour access and evacuee welfare. More than one building owner considered use of their building in evacuation as corporate social responsibility.
Schools evacuation
The interviews highlighted several examples of parents travelling unnecessarily to schools to collect children following the tsunami warning, with fatal consequences. In Tarō, parents are required to collect their children from school in the event of a tsunami warning. The school was not inundated on March 11th, but parents are said to have died while driving through the town on their way to or from the school as tsunami waves arrived. Deaths of parents and children were also reported in Kesennuma City during collection from schools. In Ishinomaki, some parents collected children from schools and lost their lives while driving through an inundated zone, whereas the children who remained at those schools survived on upper floors of the buildings.
At Unosumai, Kamaishi City, all children successfully evacuated the Kamaishi Higashi Middle School and Unosumai Elementary School, located 800 m inland from the pre-tsunami shoreline following the earthquake. Tsunami evacuation training had been conducted in Kamaishi schools since 2005 and 5-10 hours of annual class time was spent on learning about the tsunami hazard (D. Harding and B. Harding, 2011; MSN Sankei News, 2011). Due to the unexpected height of the tsunami, the children abandoned plans to stay on the 3rd floor of their school building to evacuate uphill, and then had to relocate further uphill twice more during the event. Their training had stressed that they should assess the situation as they see it and be able to respond to changing events, and this most likely saved many lives on March 11th. This is an excellent example of effective education in schools.
A recent study of schools disaster preparedness education in New Zealand showed that there is no requirement for tsunami exercises in schools, and although most schools understand their responsibility to care for their students until parents or an appropriate guardian collect them, many schools (including in coastal locations) have not carried out drills (Johnson, 2011). There is also no specific advice around the actions of parents following an earthquake – i.e. collection of students from school, or organised rendezvous at a specified safe location.
In the United States, FEMA advice states:
If the school evacuation plan requires you to pick your children up from school or from another location. Be aware telephone lines during a tsunami watch or warning may be overloaded and routes to and from schools may be jammed.” (FEMA, 2011)This advice makes no mention of the potential that parents may have to travel throughpotential inundation zones to get to or from the school. Education in Washington encouragesparents to travel to the schools designated assembly point rather than collecting childrendirectly from school.
tsunami tendenko –
In Kesennuma the disaster prevention official we interviewed believes that people should be encouraged to help others in the stages of disaster preparation and post-evacuation, rather than during the event when they should be concentrating on evacuating the hazard zone themselves. In this way, people would be encouraged to not return or travel through evacuation zones to help people prior to imminent tsunami arrival. He is consideringadopting the tsunami tendenko philosophy that was taught in Iwate Prefecture and attributedto successful evacuations of schools in Kamaishi City.
These examples are important for Washington and New Zealand to consider, as delays in evacuation are likely to cause many deaths in a local tsunami event, and education should be put in place specifically to reduce this potential issue. Adoption in Washington and New Zealand of a tendenko-like strategy encouraging self-evacuation and not stopping to help others would be a significant change from current advice, which emphasises the importance of immediate evacuation but does not explicitly advise “leave others behind” or “look after only yourself”. In fact, advice from FEMA (2011) states the opposite, which may result in further deaths from people remaining in the inundation zone too long:
“Remember to help your neighbors who may require special assistance - infants, elderlypeople, and individuals with access or functional needs.”