On the weak impact of the 26 December Indian Ocean tsunami on the Bangladesh coast M. Ioualalen1, E. Pelinovsky2, J. Asavanant3, R. Lipikorn3, and A. Deschamps1 1Geosciences Azur, IRD-CNRS-UPMC-UNSA, Villefranche-sur-mer, France 2Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia 3Department of Mathematics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
Abstract. The 26 December 2004 Indian Ocean tsunami damaged severely most of the
Gulf of Bengal's coastal areas, but the coast of Bangladesh which stands at
the edge of an extraordinarily extended continental shelf. This latter
feature has been built through huge discharges of river sediments along the
Brahmaputra and Ganges rivers. As a result of this enormous discharge,
another interesting feature of the area is the deep underwater Canyon,
connected with the estuaries, running NE-SW from 25 km off the coast towards
the continental slope.
We investigate here how these two geological features may have
modified/perturbed the Indian ocean tsunami propagation and impact on the
Coast of Bangladesh. For that purpose we have realized an ensemble of
numerical simulations based on Funwave Boussinesq numerical model and a
validated coseismic source. It is found, at first order, that the extended
shallow bathymetric profile of the continental shelf plays a key role in
flattening the waveform through a defocussing process while the Canyon delays
the process. The wave evolution seems to be related at first order to the
bathymetric profile rather than to dynamical processes like nonlinearity,
dispersion or bottom friction.
Citation: Ioualalen, M., Pelinovsky, E., Asavanant, J., Lipikorn, R., and Deschamps, A.: On the weak impact of the 26 December Indian Ocean tsunami on the Bangladesh coast, Nat. Hazards Earth Syst. Sci., 7, 141-147, doi:10.5194/nhess-7-141-2007, 2007.