Seismic Microzonation and Integrated Vulnerability Assessment of Seoul using Geotechnical and Social Indicators

Seoul, as one of the world's most densely populated cities, is increasingly vulnerable to seismic risks due to its aging infrastructure and concentrated population. This study presents a GIS-based seismic vulnerability assessment integrating geotechnical and social indicators to provide a robust framework for disaster preparedness and risk mitigation. Geotechnical datainclude stratigraphy and SPT measurements that were pre-processed to develop shear wave velocity (Vs) profiles and estimate bedrock depth (H). Social indicatorsencompass the spatial distribution of old adults and young children'spopulations as well as structurally vulnerable buildings. To ensure comparability across datasets, normalization and Principal Component Analysis (PCA) were employed, assigning weights to each indicator based on variance contribution. The resulting seismic vulnerability index was classified into five grades, ranging from very low to very high vulnerability.
The analysis identifies high-priority zones, particularly in urban centers and northeastern regions, where the confluence of deep alluvial deposits, low Vs values, and high densities of old buildings and elderly populations exacerbates seismic vulnerability. Conversely, low-risk zones, primarily in southeastern areas, are characterized by modern infrastructure compliant with updated seismic design standardsand more favorable geotechnical conditions. This study emphasizes the importance of integrating structural and demographic factors in urban seismic risk assessments. The developed methodology offers actionable insights for urban planners and policymakers to prioritize seismic retrofitting and infrastructure investments. Adaptable to other urban regions, this approach sets the foundation for incorporating real-time data to enhance the robustness of future seismic vulnerability assessments.

Keywords: Seismic microzonation, Seismic vulnerability assessment, Geotechnical indicators, Seismic resilience.