Analysis of Tsunami Evacuation Caused by the Great East Japan Earthquake: A Case Study of Ibaraki Prefecture

Abstract

This study characterizes evacuation behavior in Ibaraki Prefecture in the aftermath of the Great East Japan Earthquake and tsunamis based on geographic information, questionnaires, and interview surveys. We identified several factors on which the starting time of evacuation depended, including awareness of evacuation warnings, understanding of anticipated tsunami inundation areas (hazard maps), and distance from anticipated inundation areas. We found that those who were aware of evacuation sites, hazard maps and/or anticipated inundation areas maps, and who lived in inundated areas tended to evacuate earlier. Conversely, many residents delayed their evacuation because they chose to go home and take care of their family first. To improve future responses to likely threats, evacuation behavior and local disaster management plans must be reviewed based on the knowledge gained from this disaster.

Tsunami Risk and Alert Perceptions in Five Municipalities bordering the French Mediterranean Basin

“…People declaring locking houses when they feel ground shaking vary from 14% to 26% (Cerase et al, 2019), but this has reached 52% during the 2014 event (Goto et al, 2020) or 59% during the 2018 event (Harnantyari et al, 2020). During the 2009 Samoa event, 37% declared they were waiting for family news before evacuating, and 24% for neighbors (Lindell, 2015), while 11% evacuated seeing the neighbors running during the 2011 Japan event (Murakami et al, 2012). In the latter study, they also showed that only 3% evacuated when they see an anormal sea movement, while 21% evacuated feeling the ground shaking.…”

“…Although ground shaking is not the only warning cue that people can notice before the arrival of a tsunami. Significant water withdrawal may also lead people to evacuate the shore but it may not be sufficient to trigger evacuation by itself (Murakami et al, 2012) and sometimes it does not happen (Bird and Howes, 2008). Feeling both ground shaking and noticing anormal sea movement can provide additional cues to the population and start evacuation movement (Mori et al, 2007).…”

“…In addition, even if very rare are the studies who analyzed reactions of the population during real alert, data show sometimes significant differences. 39% of the population decided to evacuate hearing the alerting sirens during the 2011 Japan event, but 18% evacuated without waiting alarms (Murakami et al, 2012). Receiving a visual message on media and television might improve the evacuation: 51% of the surveyed Mauritius well received the 2004 tsunami alert on their television for example (Perry, 2007).…”

“…Receiving a visual message on media and television might improve the evacuation: 51% of the surveyed Mauritius well received the 2004 tsunami alert on their television for example (Perry, 2007). But electrical or communication networks can be affected by earthquakes (Goto et al, 2011;Murakami et al, 2012). Then, these alerting tools can become insufficient.…”

“…During the tsunami on Samoa Islands, in 2009, city bells were also used, so the population were aware that a danger was arriving, but the specific tsunami signal was not used, so the part of the population who knew the signal was waiting to evacuate (Lindell et al, 2015). Even if the signals seem understandable by a great number of people, some of them also do not respect the instructions, due to denial, misunderstanding, other priorities, or due to echo phenomenon, as attested by some residents about the tsunami speakers of Yamada during the 2011 event (Murakami et al, 2012). The alerts can also be disseminated by third parties such as strangers, relatives or neighbors.…”