2011.10.25 The 2011 off the Pacific Coast of Tohoku earthquake Interviewing insights regarding the high fatalities inflicted by the earthquake Masataka Ando 1, Mizuho Ishida 2, Yoshinari Hayashi 3 and Chiharu Mizuki 4 1. Institute of Earth Sciences, Academia Sinica, 2. Japan Agency Marine Earth Science Technology 3. Faculty of Safety Sciences, Kansai University 4. Graduate School of Sciences, Hokkaido University 1
2011 m 3 historical tsunamis struck the region. Lee et al. 2011 2
Why were there so many deaths in Tohoku? Since the tsunamis of 1896, 1933 and 1960, 1. Numerous breakwaters, evacuation stairways and shelters, communication systems were constructed, and 2. Tsunami evacuation drills were carried out and hazard maps were distributed to local residents. 3
Taro, Miyako city 4
Kamaishi bay breakwater 60m high above the sea bottom 5
Disaster Management Radio Communications 1. Radio + Butteries 2. Daily use 6
Despite these constructions and preparedness efforts, the March 11 Tohoku earthquake caused numerous fatalities. 7
Evacuation behaviors Most residents did not immediately evacuate, partly influenced by results from earthquake sciences. 8
One of the interviewing sites a middle high school s gymnasium 9
10
112 Interviewees e ees Gender Female 57% Male 43% Age distributionib i 80 4% 70 18% 60 50 57% 29% 17% No 8% 10 20 30 4% 4% 9% 40 15% Inundated area? Yes 92% 11
Did you hear the tsunami warning alert? N/A 7% Wireless speakers 30% No 49% Somebody else Radio 7% 7% 12
What madepeople evacuate? TV, radio 3% Seeing tsunami 19% No evacuation 10% Own decision 38% 112 interviewees Warned by others 29% 13
Iwate prefecture Comparison of death ratios between bay and headland areas Rikuzen Takata city Takata 7,621 Hirota+ Otomo 5,262 2 km 14
White beach and Pine grove ( 白砂青松 ) 15
Takata before the earthquake 16
Rikuzen Takata city 50m City hall 17
Before City Hll Hall Culture Center After 18
Before City Office After 19
Tkt Takata, Bay area 1000m 1km 20
14:40 Observed Tsunami 46: Origin time JMA tsunami warning 49 Large Tsunami iwarning (3 (>3m) 14:50 53: OBPG 2m Seafloor OBPG pressure gage 15:00 00: OBPG 5m 15:10 14: Warning renewed >6m 15:20 25: major tsunami, 15:30 Sanriku 30: Warning OBPG Renewed (>10m) 15:40 15:50 45: major tsunami, Sendai 21
Ocean Bottom Pressure Gage 14:40 46: Origin time 14:50 53: OBPG 2m 49 Large Tsunami iwarning (3 (>3m) 15:00 00: OBPG 5m 15:10 14: Warning renewed >6m 15:20 15:30 25: major tsunami, Sanriku 15:40 15:50 45: major tsunami, Sendai 22
Hirota and Otomo Rikuzen Takata Tkt 23
Death ratios of 7 subdivisions in Rikuzen Takata city 25.0 % 20.0 15.0 10.0 5.0 0.0 Takata, Bay area Hirota oaand doo Otomoo headland area 24
Tsunami advisory, tsunami warning and major tsunami warning issued by JMA in the last 4 years 2007 2008 2009 2010 Peru, Mw8.0 Tokachi, Mw6.7 Samoa, Mw7.9 Chile Mw8.5 22cm, 12h 18cm, 1.5h 15h 36cm, 6h 106cm, 24h Sakhalin, Mw6.2 0cm, 0.8h Fukushim, Mw6.9 23cm, 1.5h Okinawa, Mw6.2 0cm, 0.6h, SS Okinawa, Mw7.0, 13cm, 1.5h, SS Niigata, Mw6.7 32cm, 1h Okinawa, Mw6.6 0cm, 0.9h, SS Okinawa, Mw6.5 0cm, 1h, SS Okinawa, Mw6.4 0cm, 1h Shizuoka, Mw6.5 36cm, 1h, SS Noto, Mw6.6 6 22cm, 2h New Guniea, Mw7.6 36cm, 5.5h Kurile, Mw8.1 43cm, 8.5h 25
Means of evacuation Bicycles 5% Cars walk 16% No 10% Walk 39% About 50 % of survivors used cars for evacuation, which caused sever traffic jams and a number of tsunami victims. Cars 30% 26
Evacuation behaviors Residents are unwilling to evacuate since they believed tsunamis rare. Many residents started evacuating after seeing or knowing tsunami approaching. Many cars were used for evacuation: which were sometimes effective, but in most cases caused fatal traffic jams. 27
Responsibility of earthquake scientists Incorrect earthquake forecast based on a short history Oversight of the large slip deficit on the plate interface Current observation systems and abilities were not fully used for tsunami warning 28
Concluding remarks 1. The earthquake magnitudes and their hi resultant hazards assessed and publicized by the government are smaller presence to give rise compared to what occurred. 2. The first tsunami warning issued was for 3m in Iwate and Fukushima and 6m in Miyagi. yg This was the only warning that 44% of the interviewees received due to theimmediate destruction of the regional power supply. 29
3. The JMA had issued 16 warnings or alerts of tsunamis for Japan s islands in the last 4 years. These frequent warnings with overestimated tsunami height influenced the behavior of the residents. 4. 50 % of the local residents above 55 years old experienced the 1960 Chile tsunami, which was significantly smaller than the March 11 tsunami. This sense based on their previous experience put their lives at very high risk. 30
5. Some inhabitants assumed, with the presence of a breakwater, only slight flooding would occur and moving to the second floor at home was sufficient. 6. Many interviewees did not understand the generation of tsunamis. Some people did not react immediately evacuate to safer areas. Young children should be taught about the basic mechanism of tsunami generation 31