Tsunami multi-hazard modelling in the Indo-Lankan-Andaman Arc and coastal resilience

• Investigation of tsunami multi-hazards in the Indo-Lankan-Andaman Arc. • Numerical modelling of linear and non-linear water waves for hazard analysis. • Estimation of overall tsunami hazard using a multi-criteria decision-making framework. The Sumatra subduction zone (SSZ) poses a significant tsunami hazard to the eastern coast of India, Sri Lanka, and the Andaman-Nicobar Islands (Indo-Lankan-Andaman Arc -ILA). This study uses advanced numerical modelling to assess the potential impact of worst-case-scenario tsunamigenic earthquakes (Mw 8.8 - 9.3) originating from SSZ. The Method of Splitting Tsunami (MOST) is used to simulate ocean floor deformation, wave propagation, and coastal inundation. Tsunami multi-hazard (TMH) parameters, including wave height, velocity, arrival time, and inundation, are evaluated for 75 locations in ILA. The Analytical Hierarchy Process (AHP) in a Multi-Criteria Decision-Making Analysis (MCDMA) framework is used to rank the overall TMHs in the regions as low, medium and high. Results indicate that parts of Sri Lanka (Trincomalee, Puttalam and Panama) and Andaman-Nicobar Islands (North, Little and Great Andaman, Nicobar, and Port Blair) are highly exposed to TMHs with expected wave heights, velocity and coastal flooding ranging between 8–15 m, 32–130 km/hr and 60 - 80 km 2 , respectively. The largest tsunami waves could reach these areas in under 2.5 h. However, other parts of Andaman and Nicobar Islands, Sri Lanka, and Tamil Nadu are moderately exposed to TMHs. Whereas most locations in Andhra Pradesh, Odisha, and West Bengal fall under the low-hazard category, there are certain exceptions due to the coastal geomorphology and geometry. The findings can significantly contribute to disaster preparedness, coastal and ocean engineering, resilience measures, development of tsunami hazard maps and early warning systems.