In this sense, the government policy of designing coastal protection is for the 150 year tsunami level, the so-called ‘Level 1’ or ‘Prevention Level’, ensuring that coastal protection will prevent tsunamis from penetrating inland to protect lives and properties (or economic activities). As observed in the tsunami fragility curves, structures were especially vulnerable when the local flow depth exceeded 2 m, while a 6 m flow depth would cause everything to be washed away. Also, the central government decided a policy of coastal protection such as seawalls and breakwaters [45], which would be designed to ensure their performance to a potential tsunami level of up to the approximately 150 year recurrence interval. Note that ‘Tsunami Tendenko’ is not an egoistic maxim, with the importance of trust among loved ones to achieve the aim of maximizing the number of lives saved [17]. JMA prepared a pre-conducted tsunami propagation simulation database for over 100 000 earthquake scenarios around Japan. Using the video taken by a resident from the top of the reinforced concrete (RC) building in Onagawa harbour, the flow velocity of the tsunami inundation in Onagawa town when the houses in the town started being washed away was estimated as 6.3 m s−1 for the ascending tsunami and 7.5 m s−1 for the return flow at a flow depth of approximately 5 m. This observation implies, as the flow conditions of the subcritical flow of the ascending tsunami and the super-critical flow of the return flow, that the return flow in the first tsunami attack was slightly stronger than the leading tsunami. Among the Japanese Pacific coasts from Hokkaido down to Okinawa, the Sanriku Coast suffered the most serious damage. In coastal cities, people knew what to do next: run to higher ground. It was centered about 80 miles offshore, and tsunami warnings went up immediately. The tsunami was predicted to hit Tuvalu at 1.30am. (b) The map of tsunami inundation extent in the 2011 event (www.gsi.go.jp). The tsunami run-up height reached up to 40 m in Iwate prefecture. At least 50 min elapsed after the earthquake before the tsunami attacked the school. 129 0 obj <>stream The tsunami run-up height reached up to 40 m in Iwate prefecture. In Japan, sadly, evidence of the 2011 tsunami is easy to find. Before the 2011 event, the general belief of a safe place to survive a tsunami attack was robust RC buildings. This manual recommends hazard maps not only for residents but also for companies and fishermen. One option was a hill with a steep slope behind the school, which looked difficult for small children to climb. Japan earthquake, tsunami and Fukushima nuclear disaster: 2011 review. On 11 March, 2011 a devastating tsunami triggered by a Mw 9.0 earthquake struck the northern Pacific coast of Japan, and completely destroyed many coastal communities, particularly in Iwate, Miyagi and Fukushima prefectures. (Online version in colour. Onagawa town, Miyagi prefecture (10 014 population before the earthquake), is one of the towns devastated by the 2011 Tohoku earthquake tsunami. Having said that, the type of tsunami it produced was pretty much the same, but with wave heights certainly not expected to exceed 3.0 metres and actually appearing to not exceed about 1.5 m in the … Tsunami safety has been a focus of coastal city planning throughout the nation. When the earthquake severed the connection between the nuclear power plant and the Japan electrical grid, the diesel backup system turned on as it was supposed to. The earthquake and subsequent tsunami that struck northeastern Japan on March 11 was perhaps the most widely recorded natural disaster in human history. The seawall was designed for Level 1 tsunami (the height equivalent to the historical tsunami heights in the past 150 years and storm surge heights in the past 50 years). Field measurements of extreme inundation are now used for validating numerical models [8,9]. H�l�I��6��>�/���i�E�#. In April 2011, one month after the event occurred, the central government established the Reconstruction Policy Council to develop a national recovery and reconstruction outlook for tsunami-resilient communities [43,44]. In December 2011, the central government enacted the ‘Act on the Development of Tsunami-resilient Communities’. (b) The extent of the tsunami inundation zone with the measurement of the run-up heights at tsunami inundation limit in Sendai Coast [23].Download figureOpen in new tabDownload powerPoint. Figure 3. This 18 m tall lighthouse built on a cliff 10 m a.s.l. Japan has invested heavily in coastal protection and buildings that can withstand tremors. March 11, 2011 | Infant, Reader's Picks, School Age, Teens, … Following the expanded seismic/tsunami monitoring network by installing broadband seismometers and offshore tsunami monitoring systems, JMA's tsunami warning increased its capability for quicker and more accurate estimation of earthquake magnitude and tsunami. This problem is not yet solved. The maps seem quite similar in terms of the tsunami inundation extent. The radio station broadcast the tsunami warning at 10pm local time last Friday, after the earthquake in Japan. Seawalls or coastal structures should be designed with the assumption of overtopping and resiliency, and communities should not rely on coastal infrastructures alone for protection. 2. … Figure 2 illustrates the measured tsunami inundation and run-up heights by the survey team, with plots of historical tsunami heights of the 1611 Keicho Sanriku, 1896 Meiji Sanriku, and 1933 Showa Sanriku earthquake tsunamis [24]. The seawall is designed with reference to Level 1 tsunami scenario, while comprehensive disaster management measures should refer to Level 2 tsunami for protection of human lives and reducing potential losses and damage. These principles are now highly valued as one of best practice/outcome of disaster education. However, its size was unexpectedly large (Mw 9.0). Text by: RFI Follow 2 min. The solid lines are obtained from the devastated municipalities of Miyagi prefecture (from the 2011 event) and the dashed one is from Banda Aceh, Indonesia (the 2004 Indian Ocean tsunami) [37]. On this basis, the maximum potential earthquake in the Tohoku region was estimated as Mw 8.5. East of Japan, the Pacific plate dives beneath the overriding Eurasian plate. Prof. Katada's three principles: not to trust hazard maps (recognize the predictive limits), make the best efforts in any situation and take the initiative of evacuation in a community; these are highly recommended attitudes to overcome a disaster that exceeds all worst-case scenarios. This also means less effort is spent trying to establish the details of past tsunami events. Revisiting the modern histories of Tohoku tsunami disasters and pre-2011 tsunami countermeasures, we clarified how Japan's coastal communities have prepared for tsunamis. On the other hand, a hazard map can function to assure residents living outside of the expected inundation zone that their area is NOT at risk. In 1997, the Japan central government council, which consists of seven ministries, issued a guideline for comprehensive tsunami countermeasures that should be taken as part of regional tsunami disaster prevention. Figure 4. Lastly, public education is the most important part of tsunami disaster management. In fact, its tsunami forecasting technologies and numerical models were exported to many foreign countries that needed support, such as Indonesia, Thailand, Mexico and Peru. Tohoku University's School of Engineering and the Japan Nuclear Energy Safety Organization (JNES). High rise RC buildings with robust columns and walls can withstand tsunami flow depths over 2 m and can be used for vertical evacuation. Now, JMA has expanded its seismic/tsunami monitoring network by installing broadband seismometers and an offshore tsunami monitoring system, to increase its capability for quicker and more accurate estimation of earthquake magnitude and tsunami [21]. 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