Preservation potential of 2004 Indian ocean Tsunami sediment in low-lying areas, Changwat Phuket

After the 2004 Indian Ocean tsunami event, studies on tsunami deposit has increased. Preservation potential of tsunami sediment, which is evaluated from their sedimentary structures and thickness (Szczucinski, 2012), is of the utmost importance for estimation of recurrence intervals of tsunamigenic earthquakes. A low preservation of tsunami deposits in the geological record may lead to an underestimation of tsunami hazard (Spiske, 2013). Phuket was one of the areas most affected by the 2004 tsunami event. Although tourism is developed in the coastal areas and may disturb the tsunami deposit and its preservation, we found a 3 to 20 cm layer of sand which was interpreted as 2004 tsunami deposit in Layan Lagoon and Laguna area. These sand layers consist of fine to coarse sand, normal grading, mud rip-up clasts, sharp basal contact and few shell fragments. The 2004 tsunami deposit is underlain and overlain by fine-grained sediments commonly deposited by suspension in the lagoon which lead to high preservation potential of tsunami sand layer. In contrast, the low potential area is represented by the Bangtao area. The preservation potential depends on depositional environment (e.g. lagoon or plain), climate (e.g. arid or tropical) and anthropogenic modification such as land development for tourism or tin-mining. It is found that the sedimentation rate in Layan Lagoon and Laguna area are 2.2 cm/yr and 2.5 cm/yr, respectively.