As the December 2004 tsunami made painfully clear, there is no tsunami warning system in the Indian Ocean. There has been no impetus for a warning system prior to this event because there are very few known historical or geologic records of previous tsunamis in this part of the Indian Ocean, and therefore no estimates on the frequency of such events. Onshore, the 2004 tsunami deposited sand in a variety of marshy environments, and, given the proximity of the Sumatran trench to the West, it seems highly likely that large pre-historic tsunamis affected this region and left behind similar sedimentary records. The existence of the 2004 tsunami deposit provides a unique opportunity to find such a record of these tsunamis. The PIs will carry out a project to locate and core suitable sedimentary traps along the Andaman coast of Phuket Island - traps that should have captured a long term record of tsunamis derived from earthquakes along the Sumatran Trench. However, the coastal sites they have identified all lie within rapidly developing tourist areas where resort development has accelerated in the post-tsunami period, and now threatens to destroy the most promising paleotsunami sites. Resort development makes airfares cheap and usually makes for easier access (roads, infrastructure, etc.) - but in this case, it also threatens the study sites themselves. This project is identifying suitable, primarily muddy, sedimentary environments within the 2004 inundation zone where preservation of tsunami deposits is most likely. The surficial geology and topography at each site is mapped using differential GPS. Cores from these sites are collected using a Livingstone piston corer capable of capturing cores up to 5 m long. Cores are analyzed using a variety of sedimentary, chemical and physical criteria to identify any paleotsunami deposits, and to document the Holocene history of the region. Key samples are extracted from the cores for 14C dating. This project will verify the existence of paleotsunami deposits in coastal marshes of Phuket and provide a preliminary Holocene depositional chronology for the Andaman region. The impact of the 2004 tsunami was devastating to Thailand. Efforts to understand the future tsunami hazard depend on knowledge of the prehistoric tsunami chronology. In particular, the documentation of previous tsunamis will help dispel the myth that this was a one-time-ever event, and lend momentum to tsunami hazard preparation along the densely populated and rapidly developing Andaman coast. In addition to the appropriate international peer-reviewed journals, the PIs will publish results in local Thai publications, and present the results at conferences in Thailand. At least one CSUF student will be involved in the core analyses. Thai students (funded by Chulalongkorn University) will also participate in the field work. This will be a collaborative project with Thai scientists who will gain new expertise in the sampling and analysis of Holocene sediment, an expertise they currently lack. The continuation of international goodwill, understanding and cooperation will be a significant impact of this project both at CSUF and in Thailand.
