Comparative Analysis of Tsunami Casualty Estimation Approaches: Agent-Based Modeling versus Simplified Approach in Japanese Coastal Cities

Abstract Estimating potential casualties from a significant earthquake and tsunami event is crucial to enhance disaster preparedness and response. Although various approaches exist to assess potential casualties, few studies have made direct comparisons between them. The present study aimed to clarify the differences in the estimation of casualties between an agent-based model (ABM), which can capture detailed evacuation behavior but demands significant computational resources, and a simplified approach at less computational cost by assuming that evacuees would move along a straight line from their initial location to the closest evacuation destination. These different approaches were applied to three coastal cities in Japan—Mihama, Kushimoto, and Shingu in Wakayama Prefecture—revealing significant differences in the estimated results between the ABM and the simplified approach. Notably, when the effects of building collapse due to an earthquake were considered, the mortality rates estimated by the ABM were higher than those estimated by the simplified approach in the three cities. There were also significant differences in the spatial distribution of the estimated mortality rates between the ABM and the simplified approach. The findings suggest that while the simplified approach can yield results more quickly, casualty estimates derived from such models should be interpreted with caution.