Tsunami hazard assessment of Indian coast

Abstract

The tsunami caused by the magnitude 9.1 Andaman–Sumatra earthquake in 2004 brought into limelight the vulnerability of Indian coast against the flooding hazard due to this natural phenomenon. The paper brings out the work carried out in relation to assessment of tsunami hazard along the Indian coast following a deterministic approach based on the method suggested by Japan Society of Civil Engineers. The tsunamigenic source zones around Indian coast are identified, and maximum tsunamigenic earthquake magnitude from each source zone, viz. Burma–Andaman–Sumatra, Makran and zone of diffused seismicity, is estimated. Several scenario earthquakes are postulated from each zone accounting for uncertainties in fault strike and dip. Tsunami hazard from these zones to Indian coast is estimated based on validated numerical tools at a grid spacing of 300 m, and hazard is presented in the form of maps. Important phenomena such as wave amplification in shallow waters and wave runup are captured in the analysis. The water levels are represented in terms of mean estimates and associated standard deviations in estimates reflecting uncertainty in evaluated levels. The assessment indicates higher vulnerability of the east coast and the southwestern coast of India as well as existence of several tsunami hot spots (regions with unusually high wave amplitude) along the Indian coast. In addition to increased understanding of tsunami vulnerability of Indian coast, the tsunami hazard maps presented in the paper will be useful during planning and engineering of coastal structures and infrastructure in selection of their safe grade elevations. The work presented here can be further enhanced by addressing uncertainties in maximum earthquake magnitudes, related rupture parameters and with better shallow water and coastal topography data.