Nearshore tsunami amplitudes off Sri Lanka due to probable worst-case seismic scenarios in the Indian Ocean

This paper describes a deterministic assessment of the tsunami hazard to Sri Lanka from all active subduction zones in the Indian Ocean Basin. High resolution numerical simulations of tsunami propagation have been carried out for eight plausible maximum-credible seismic scenarios in Northern Sumatra-Andaman, Southern Sumatra, Arakan and Makran subduction segments. The numerical results have been analyzed to obtain wave arrival times and maximum tsunami amplitudes just off the coastline of Sri Lanka. A sensitivity analysis carried out at the outset indicates that the computed tsunami amplitudes off Sri Lanka are only marginally sensitive to the perturbations in the source parameters. Moreover, the computed values of peak tsunami amplitudes and arrival times corresponding to an event similar to the tsunami in 2004 are in good agreement with the respective field observations. The numerical simulations also suggest that the maximum tsunami amplitudes around the coastline of Sri Lanka corresponding to worst-case scenarios in Southern Sumatra, Arakan and Makran seismic zones are only less than about 20-30% of those due to the same in Northern Sumatra-Andaman segment. This means that an event similar to the 2004 tsunami in the Northern Sumatra-Andaman subduction zone could be considered as the worst-case seismogenic tsunami scenario for any part of the coastline of Sri Lanka. The information presented in this paper would help authorities responsible for evacuation to make a better judgement as to the level of probable maximum tsunami heights in different areas along the coastline of Sri Lanka, and act accordingly, if a large earthquake were to occur in any of the subduction zones in the Indian Ocean Basin. (C) 2012 Elsevier B.V. All rights reserved.