Migration as a Hidden Risk Factor in Seismic Fatality: A Spatial Modeling Approach to the Chi-Chi Earthquake and Suburban Syndrome

Abstract. Suburban areas have disproportionately experienced higher fatalities during major earthquakes. Place-based models attribute this spatial disparity to hazard, exposure, and social vulnerability factors. However, the impact of migration on seismic fatality remains underexplored, primarily due to the challenges in accessing mobility data. In this study, we apply a geospatial method, the radiation model, to estimate migration patterns as a critical component of exposure and vulnerability. Analyzing the 1999 Chi-Chi earthquake in Taiwan with Poisson regression across 4,052 neighborhoods, we factor in migration inflow (i.e., population traveling from other neighborhoods), migrants' origin income, and indigenous population percentage among migrants, along with other risk factors proven in previous studies. Our findings indicate that migration inflow significantly correlates with increased fatalities. Furthermore, a lower income at the migrants' origin neighborhood is significantly associated with higher fatalities at their destination. An elevated proportion of indigenous population in the migrants' origin neighborhood also significantly correlates with increased fatalities, although the impact of the Chi-Chi earthquake does not predominantly affect indigenous jurisdictions. This study underscores the seismic fatality risk in the outskirts of megacities, where migrants from lower income and historically marginalized groups are more likely to reside for precarious employment conditions, emphasizing the need for affordable and safe living infrastructures for the migrating population. Addressing migrants’ vulnerabilities in housing will not only reduce seismic fatality risk but also improve preparedness against other disasters and public health emergencies.