Sediment characterisation of the 26 December 2004 Indian ocean tsunami in Andaman group of islands, bay of Bengal, India

Abstract

The large tsunami, which was generated by an earthquake on 26 December 2004, affected most of the countries around the Indian Ocean. A total of 48 tsunamigenic surface sediments have been collected from various coastal geomorphological features such as beaches, estuaries/creeks and mangrove areas in the Andaman group of islands. These samples were analysed for sediment characteristics such as sediment texture, granulometric studies. The studied tsunamigenic sediments, deposited by the 26 December 2004 tsunami in the Andaman group of islands consist of poorly sorted, coarse sand to medium sands, and are similar to depositional effects of previously reported earthquake-generated tsunami waves. The tsunamigenic sediment consists of a coarse sand layer with abundant reworked shell and other carbonate fragments. The tsunami sediments were mainly composed of boulders of corals and sand which determines the high-energy environment throughout the study area. The variation in Ф mean size, therefore, reveals the differential energy conditions that lead to the deposition of these kinds of sediments in different locations. The tsunamigenic sediments were mainly poorly sorted, moderately well sorted and well sorted during the post-tsunami (2005) and whereas they were mainly moderately well sorted to well sorted during the post-monsoon (2008). The symmetry of the samples varies from strongly fine skewed to strongly very coarse skewed in the post-tsunami (2005) and post-monsoon (2008). The Kurtosis of the tsunami sediments were mainly Platykurtic, Mesokurtic and Lepokurtic during the post-tsunami (2005) and mainly Mesokurtic and Lepokurtic in post-monsoon (2008).