Variations in the 2004 Indian Ocean tsunami deposits thickness and their preservation potential, southwestern Thailand

Field surveys were conducted in March 2005 and December 2008 in southwestern Thailand to investigate local variation in the thickness and preservation potential of onshore deposits formed by the 26 December 2004 Indian Ocean tsunami. The 2008 survey results revealed that the thickness of deposits varies by a few centimeters in pits located less than 10 m apart because of local undulation of the topography and possible bioturbation. At 13 among all 24 sites, the difference in thickness during 2005 and 2008 surveys was within the range of local variation. In fact, very thin tsunami deposits with 1 cm thickness in the 2005 survey were well preserved during the 2008 survey. Furthermore, tsunami deposits near the maximum inundation limit were found in the 2008 survey, with thicknesses that are consistent with those reported from the 2005 survey. At no site was a tsunami deposit eliminated completely. Based on these observations, we infer that the tsunami deposit thickness is well preserved, even in a tropical climate with heavy rains such as that of Thailand.