The 2016 Kumamoto earthquake consisted of a magnitude 6.2 foreshock that occurred on the 14th of April, and a magnitude 7.3 main shock that occurred on the 16th of April. The main shock occurring over the magnitude 6.2 foreshock was not anticipated because the foreshock was originally considered to be the main shock. After the earthquakes occurred, the Japan Meteorological Agency (JMA) discontinued its policy of announcing the probability of aftershock occurrences. The experience of the Kumamoto earthquake and the policy change concerning risk communication may affect the public risk perception of earthquakes, as well as the public trust toward authorities. In this study, we examined the reasons residents made the decision to evacuation both the foreshock and the main shock. Moreover, we investigated how residents perceived subsequent earthquake risk and they evaluate similarity and trust toward the authorities (the JMA, government, mass media, prefecture, and municipality). This study analyzed data from a mail survey implemented by the MEXT of Japan in the areas of the Kumamoto prefecture that were damaged by the earthquake. As a result, there were differences in the reasons for evacuation decisions between the foreshock and the main shock. Although residents decided to evacuate based on a fear of disaster in the foreshock, they decided to evacuate the main shock based on neighborhood communication. Moreover, the residents’ evacuation patterns influenced the earthquake risk perception. As well, the evacuation pattern influenced similarity toward the authorities and then reduced trusts toward the authorities. This study indicates that residents amplified the evaluations of the authorities after the earthquake. The influences of similarities toward the authorities became salient as a determinant of trust. This study reveals features of residents’ risk reactions to the earthquake, and discusses the importance of the similarity of the authorities for disaster risk communication.
Earthquake early warning for the 2016 Kumamoto earthquake: performance evaluation of the current system and the next-generation methods of the Japan Meteorological Agency
