Seismic safety resilience assessment of building clusters in megacities with refined site correction

Background Earthquake-induced cascading damage and functional failure of dense building clusters are the primary source of systemic disaster losses in megacities, yet conventional regional seismic assessments generally neglect spatial variations in local site conditions, which misrepresents ground-motion input and the resulting resilience pattern. Methods Using the time-averaged shear-wave velocity of the uppermost 30 m (Vs30) as the core site metric, spatially variable ground motions were refined through site response analysis, explicitly accounting for basin amplification, while soil–structure interaction was addressed in the refined single-building analyses. National seismic risk survey data were integrated with screened specialized datasets to construct an optimized GIS database and a three-tier “region–system–individual building” evaluation architecture; a three-dimensional indicator system covering site geology, structural safety and post-earthquake functional recovery was then applied to a core district of Beijing, China. Results Vs30-based site correction captured the spatial heterogeneity of ground motions and substantially altered the ground-motion intensity fields, raising peak ground acceleration from a baseline of 3.80 m/s2 to 5.80 m/s2 in the southeastern soft-soil subdistricts. Severely damaged or fully collapsed buildings accounted for 26.46% of the inventory, whereas 95.09% of buildings complied with the predefined resilience targets, the 4.91% that failed being concentrated in historic aged residential subdistricts overlapping thick soft soils. Refined single-building analyses ranked resilience as base-isolated RC shear-wall residential > RC frame–shear wall office > non-isolated RC-frame hospital. Conclusion Site-corrected, building-level resilience mapping provides quantitative evidence for megacity seismic planning, old-community renewal and emergency resource deployment, and shows that addressing primary structural safety alone systematically underestimates the vulnerability of critical lifeline facilities.