Evacuation Behavior in the Absence of Ground Shaking: A Survey Report on the 2025 Kamchatka Far-Field Tsunami in Shingu City, Japan

抄録

This study investigated residents’ evacuation behavior in Shingu City, Wakayama Prefecture, following the far-field tsunami generated by the 2025 Kamchatka Peninsula earthquake. Using a web-based questionnaire survey (N=283), the relationship between residents’ spatial risk perception and evacuation actions in the absence of ground motion was analyzed. The results revealed that official information, specifically Tsunami Advisories, Warnings, and Evacuation Orders, served as the primary trigger for 81% of evacuees, confirming that information interpretation dictates behavior during far-field tsunamis. The evacuation rates of residents who perceived themselves to be inside the estimated inundation zone were significantly higher than those for residents outside the zone. However, spatial perception did not significantly affect evacuation timing or methods. Notably, the phased issuance of warnings contributed to a wide dispersion of departure times, effectively preventing traffic congestion despite high private car usage. Conversely, the decision to return home heavily depended on subjective judgment and social cues rather than official clearance, contrasting with near-field events, where physical cues are clearer. These findings underscore the importance of risk communication strategies that not only initiate evacuation but also sustain protective behavior, preventing premature returns driven by an overestimation of safety in the absence of visible physical cues.