Biswas, Soham2026-10-132026-10-132026http://nits.ndl.gov.in/handle/123456789/233This study introduces a comprehensive, multi-scale framework for tsunami hazard assessment that combines global probabilistic forecasting, geospatial vulnerability mapping, and structural resilience analysis to guide risk-informed planning and mitigation. On a global level, a stochastic model estimates future tsunami occurrences across 14 high-risk tsunamigenic zones, using Conditional Probability (CP) and the Total Probability Theorem (TPT). This dual methodology considers both mixed tsunami conditions (any wave height) and high-impact events (wave height > 3 meters). Inter-arrival times are modelled with the best-fitting distributions, such as Gamma, Lognormal, Weibull, and Log-logistic. The tsunami-to earthquake ratio (r) is included in TPT calculations to account for spatial seismic-tsunamigenic variability. Results indicate that, under mixed conditions, the highest tsunami probabilities are in Zones 1 (Colombia, Ecuador, Brazil), 7 (Japan, China, North Korea), and 11 (Solomon Islands, Vanuatu, New Caledonia). For high-impact tsunamis, Zones 3 (Cuba, Jamaica, Haiti), 9 (Malaysia, Brunei, Australia), and again Zone 1 show the greatest risk. This probabilistic framework offers a robust basis for early warning systems and transnational preparedness. A comprehensive tsunami vulnerability assessment for India’s eastern coast was performed at the regional level, utilizing GIS-based spatial analysis combined with a multicriteria decision making framework. Six key parameters, elevation, slope, coastal proximity, land use/land cover (LULC), flow accumulation, and population density, were incorporated through the Analytic Hierarchy Process (AHP) to generate detailed vulnerability maps. These maps highlighted Nagapattinam (166.46 km²), Cuddalore (245.64 km²), Kanyakumari (37.65 km²), Karaikal (35.71 km²), and Chennai (35.63 km²) as highly susceptible coastal zones. To enhance these insights, connectivity overlays depicting major roads, railways, and high-elevation safe locations were added, offering essential guidance for emergency response and sustainable coastal development. On the structural front, the study assessed the tsunami performance of Open Ground Storey (OGS) G+2 reinforced concrete (RC) buildings, with a specific focus on retrofitted stepped column designs. Using Artificial Neural Networks (ANNs) and Monte Carlo Simulations (MCS), fragility curves were developed for three damage states: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). Compared to traditional RC frames, buildings with stepped columns showed substantial performance improvements, with about a 50% reduction in inter-storey drift and lower exceedance probabilities of 27.05% (IO), 28.57% (LS), and 32.4% (CP). Stepped-column buildings withstood tsunami wave heights of 9.4 m (IO), 11.4 m (LS), and 12.9 m (CP), while regular RC buildings failed at lower wave heights of 7.2 m (IO), 9.3 m (LS), and 10.6 m (CP). The study also compared square and circular stepped column geometries, highlighting the crucial role of column shape in enhancing tsunami resistant performance. At a 50% exceedance probability, circular columns withstood greater wave heights of 10.3 m (IO), 12.1 m (LS), and 13.6 m (CP), outperforming square columns by 9.6%, 6.1%, and 5.5%, respectively. They also exhibited reduced inter-storey drift ratios and delayed hinge formation, indicating superior ductility and energy dissipation. Although circular columns involve approximately 9% higher initial construction costs, they provide long-term economic benefits, including 5–10% reductions in overall lifecycle losses. These findings confirm that circular stepped-column retrofits offer a cost-effective and structurally resilient solution for tsunami-prone infrastructure. Overall, this study integrates global tsunami forecasting, regional hazard mapping, and performance-based structural design into a unified framework, providing practical insights for infrastructure planning, disaster preparedness, and coastal policy-making, particularly in highly vulnerable areas such as coastal India.en