Grain-Size and Thin Section Characteristics of Tsunami Sediments from Thai-Andaman Coast, Thailand

Abstract

The 2004 Indian Ocean tsunami killed more than 300,000 people and damaged the infrastructures, properties and environments of many coastal and island nations of the Indian Ocean, principally Indonesia, Sri Lanka, Thailand, India, The Maldives and the African Coast. In Thailand, the coastal provinces of Ranong, Phang Nga, Phuket, Krabi, Trang and Satun on the Andaman coast at latitude 5° to 11°N, longitude 98° to 102°E (Fig. 1) suffered 1–10 m run-up heights (Japanese Survey Team 2006). Phang Nga was the worst affected province attacked by 4–10 m high run-ups. Tsunamis cause seawater to flood onto land, creating distinctive horizontally widespread sandy deposits. Tsunami sediments from Japan are the typical sediments discussed for the historical tsunami events and the geological evidence (e.g., Minoura et al., 1996; Fujiwara et al., 2000; Sawai, 2002; Fujino et al., 2006). Tsunami waves transport sandy sediments from offshore areas and the beach and deposit sediments on the inundated land surface. Tsunami deposits are very characteristic for tsunami affected areas. A local tsunami chronology can be determined by using geological methods to identify and characterize recent and ancient tsunami events in coastal sediment sequences (Dawson et al., 1996; Dawson, 2007; Dawson & Stewart, 2007). Sediment characteristics from general coastal processes, storms, ancient and recent tsunamis have been reported from many parts of the world for distinguishing deposit types, geomorphological effects and sedimentation processes (e.g. Dawson et al., 1991; Dawson, 1994; Nanayama et al., 2000; Shi & Smith, 2003; Gelfenbaum & Jaffe, 2003; Anthony & Hequette, 2007; Morton et al., 2007; Kortekaas & Dawson, 2007). Tsunami deposits are provisionally distinguished in the field on the basis of anomalous sand horizontals, finingupward and fining-landward, coupled with organic-rich, fragmented backwash sediment (e.g. Dawson et al., 1991; Shi et al., 1995; Gelfenbaum & Jaffe, 2003; Smith et al., 2004; Srisutam & Wagner, 2009; Srisutam & Wagner, 2010a). Typically, tsunami sediments comprise medium to fine sand with small amounts of fine silt and clay (e.g. Dawson & Shi,