Tsunami evacuation: Lessons from the Great East Japan earthquake ...

2012
In Ishinomaki, we observed a map which focussed on the local landslide hazard and
evacuation routes designed for landslide only (Figure 31). This map shows evacuation
routes to shelters which are away from steep hillsides, but encourage evacuation into areas
close to the banks of the Kitakami River. On March 11 th 2011, the specified evacuation
shelters were inundated by tsunami flow from the river channel. This illustrates the need for
information boards and signs to include multiple hazards where this is appropriate.
Figure 31
Landslide hazard and evacuation map on an information board in Ishinomaki City.
2.3 Response to natural and informal tsunami warnings
2.3.1 Natural warnings
The officials interviewed in Tarō, Kesennuma, Minami-Sanriku and Natori reported that
ground shaking lasted longer than 2 minutes (most reported as long as 3 minutes) and in
Kesennuma, Minami-Sanriku and Ishinomaki the interviewees acknowledged that this
earthquake felt unusual or stronger than they had ever experienced previously (including
previous Miyagi-ken-oki events in 1978 and 2004). Most interviewees, when questioned
further, felt that they could have stood up in the earthquake and that ‘stronger’ generally
referred to the length of shaking and the long and variable period of the shaking. As a result
of the ground shaking, they recognised that this could be the recurrent Miyagi-ken-oki event
and there was recognition of the potential for tsunami. The JMA shaking intensity at each
location is given in Table 3. Drawdown of the tsunami was only cited in our interview at
Minami-Sanriku.
Public response to the natural warning of strong and long ground shaking was variable. In
Tarō, most people in the town are believed to have evacuated in response to ground shaking
and although an audible tsunami warning was broadcast by the disaster prevention officials,
this was broadcast while people were already running. Tarō Town officials describe a history
of strong communication of tsunami risk from parents to children, with a tradition of telling
stories about tsunami, education in school on tsunami including communication on the
subject between local and visiting schoolchildren. The official himself told us how he was
often told as a child to “run straight away, even if the ground shaking is small” in an
earthquake. Local tradition in Minami-Sanriku encourages evacuation from coastal areas
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