Seismic-risk mapping of existing hospital buildings from three-tier assessment method

Karachi, located in southern Pakistan, faces high seismic risk due to dense population and non-engineered construction, making it essential to keep hospitals operational before and after earthquakes. Therefore, a comprehensive three-tier methodology is employed herein to quantify the seismic risk index (SRI) of three case study code-conforming hospital buildings (hospitals 1, 2 and 3). The proposed seismic-risk mapping methodology indicates a consistent reduction in risk with higher-performance tiers. At tier 1, hospital 1 shows the highest vulnerability (SRI ≈ 14.0–14.4%), while hospital 2 (8.25%) and hospital 3 (9.16%) exhibit moderate risk. At tier 2, SRI values decrease significantly for all facilities, with hospital 3 (2.99%) and hospital 2 (3.77%) achieving the best performance, whereas hospital 1 remains comparatively weak (≈4.8–6.4%). At tier 3, seismic risk becomes negligible for hospital 2 (0.37%) and hospital 3 (0.39%), while hospital 1 shows further improvement (≈4.0–6.0%) but still requires priority intervention. Overall, the results demonstrate the reliability of the rapid visual screening-based framework for rapid seismic-risk prioritisation; however, detailed analytical assessment is recommended for final decision making. Moreover, future work should expand by employing non-linear dynamic analyses for precise response prediction, developing regional fragility models and investigating retrofit strategies to strengthen the overall resilience of healthcare systems.