A Study on the 2016 Kumamoto Earthquake: Citizen’s Evaluation of Earthquake Information and Their Evacuation and Sheltering Behaviors

Abstract

In order to reveal the current status and issues of the victims of the 2016 Kumamoto Earthquake eight months after its occurrence, we conducted large-scale random sample questionnaire surveys with victims aged 18 and over in the most affected municipalities from November to December 2016. We decided to sample a total of 7,000 victims (1,600 from Kumamoto City and 5,400 from the other thirteen municipalities) with an expected collection rate of 25% and a sampling error of 5%; 3,272 victims effectively responded to the questionnaires (effective collection rate: 46.7%). The Kumamoto Earthquake was a series of earthquakes including foreshocks and main shocks of magnitude 7 on the Japanese seismic intensity scale, and aftershocks that appear to have significantly influenced the victims’ response behaviors as well as the recovery and reconstruction of the affected areas.The questionnaire survey on whether the victims’ pre-earthquake knowledge and awareness had any influence on their post-earthquake behaviors reveals that not more than 30% were aware of the active faults present in their areas before the earthquake occurred and that half of them hoped that no earthquakes would occur. On the other hand, the victims who were aware of the active faults present in their areas and who were afraid that an earthquake could occur within 10 years had planned accordingly and had stocked the necessary goods and provisions.The questionnaire survey on how the victims behaved in the event of the foreshocks and main shocks reveals that about half of them evacuated and found shelter after the foreshocks. Those who feared any aftershocks, and the damage to their buildings due to the aftershocks, evacuated and took shelter. Those whose buildings were not damaged and whose lifelines were available did not evacuate or take shelter. After the main shock, about 70% of the victims evacuated and took shelter because, in addition to their fears of the aftershocks, their buildings were actually damaged and their lifelines had been rendered unavailable.The questionnaire survey on whether the victims’ pre-earthquake knowledge and awareness had any influence on their post-earthquake behaviors reveals that in the event of an earthquake, like in the case of the foreshocks of the Kumamoto Earthquake in which human beings and buildings were not so scathed and people could not decide whether to evacuate or take shelter, those with more pre-earthquake knowledge and with awareness of earthquake damage better anticipated the aftershock occurrences. On the other hand, in the event of the main shocks of the Kumamoto Earthquake, in which there was great damage to humans and buildings, people with or without pre-earthquake knowledge and awareness on earthquake damage were urged to evacuate and take shelter.The questionnaire survey on whether aftershock information was properly communicated to the victims reveals that they followed the information on aftershocks broadcast by TVs and radios immediately after the foreshock had occurred. The victims did not follow the Meteorological Agency’s press release on the aftershocks on the afternoon of the following day in order to get an update. Instead, they took the information broadcast by TVs and radios as “no great aftershocks would occur in the future,” which was completely different from what the Meteorological Agency’s press release intended. The questionnaire survey on the influences of the aftershock information on the victims’ evacuation and sheltering behaviors reveals that the Meteorological Agency’s press release on the following day of the foreshock occurrence stated that the probability of the aftershock occurrence of lower 6 or over on the Japanese seismic intensity scale is 20% in the following three days, and that of the aftershock occurrence of upper 5 or over on the Japanese seismic intensity scale is 40%. This seems to have had a greater influence on the behaviors of the victims who assumed that “no great aftershocks would occur in the future” as compared to the behaviors of those who assumed that “an aftershock could occur anytime in the future” and “a big aftershock might occur in the future.”With regard to the movements in the victims’ long-term post-earthquake residences and evacuation destinations, 57.5% of the total victims stayed at home after the foreshock occurrence, which is not so different from the case of the Hanshin-Awaji (Kobe) Earthquake, an inland earthquake with relatively few aftershock activities. However, the ratio of the victims who stayed at home stood at 28.7% after the main shock occurrence, at 32.8% on the first weekend or about four days after the foreshock occurrence, and at 49% in the week following the earthquake occurrence, which indicates that more victims evacuated and sought shelter outdoors in cars, tents, and vacant grounds as seen in the case of the Mid-Niigata Earthquake, which witnessed many aftershock activities. Therefore, the evacuation behavior pattern in the Kumamoto Earthquake may be regarded as a cross between the Hanshin-Awaji (Kobe) Earthquake and the Mid-Niigata Earthquake.