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Suburban areas have experienced disproportionately more 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 of 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 4052 neighborhoods, we factor in migration inflow (i.e., population traveling from other neighborhoods), income of the migrants' origin, and the indigenous-population percentage among migrants, along with other risk factors proven in previous studies. Our findings indicate that migration inflow significantly correlates with an increased number of fatalities. Furthermore, a lower income in the neighborhood of the migrants' origin is significantly associated with more fatalities at their destination. An elevated proportion of the indigenous population in the migrants' original neighborhood also significantly correlates with an increased number of fatalities, although the impact of the Chi-Chi earthquake does not predominantly affect indigenous jurisdictions. This study underscores the seismic-fatality risk on the outskirts of megacities, where migrants from lower-income and historically marginalized groups are more likely to reside for precarious employment, emphasizing the need for affordable and safe living infrastructure 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.

While disaster studies researchers usually view risk as a function of hazard, exposure, and vulnerability, few studies have systematically examined the relationships among the various physical and socioeconomic determinants underlying disasters, and fewer have done so through seismic risk analysis. In the context of the 1999 Chi-Chi earthquake in Taiwan, this study constructs three statistical models to test different determinants that affect disaster fatality at the village level, including seismic hazard, exposure of population and fragile buildings, and demographic and socioeconomic vulnerability. The Poisson regression model is used to estimate the impact of these factors on fatalities. Research results indicate that although all of the determinants have an impact on seismic fatality, some indicators of vulnerability, such as gender ratio, percentages of young and aged population, income and its standard deviation, are the important determinants deteriorating seismic risk. These findings have strong social implications for policy interventions to mitigate such disasters.