Browsing by Author "Williams, SP"

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    Assessing tsunami signatures in the geologic record for long-term risk evaluation, Samoan Islands
    (American Geophysical Union, 2011-12-05) Williams, SP; Goff, JR; Davies, TR; Cheung, KF; Yamazaki, Y; Chagué-Goff, C; Prasetya, G; Wilson, T
    Recent tsunamis worldwide have prompted significant efforts amongst scientific and disaster management authorities to enhance understanding of these processes, and further mitigate their immediate to long-term impacts. The tsunami of 29 September, 2009, which impacted the Samoan Islands, prompted local demand to improve long-term understanding of the risk these processes have on local communities and environment in general. This research aims to address some of this demand through an inter-disciplinary investigation of tsunami (and cyclone) deposits in the Samoan geologic record. The use of tsunami deposit investigations has become a key component in tsunami hazard assessments globally, as they enable long-term understanding of tsunami risk to communities and property, including loss of life. In the Samoan Islands, historical records of tsunamis are meagre and only date back to 1837 AD. This project enables tsunami records to be extended into Samoan pre-history, thereby forming an information basis for long-term risk mitigation in these islands. It also provides an avenue for establishing a suite of multi-proxy criteria for identifying and distinguishing tsunami and cyclone events specific to Samoa. Further, it provides the opportunity for starting to understand likely source and wave characteristics associated with identified tsunamis. In this paper, we provide a discussion on the applications and implications of results yielded thus far in the project to understanding long-term tsunami risk in the Samoan Islands. Current interpretations of empirical stratigraphies, semi-quantitative X-ray fluorescence spectroscopy analysis, geochronology analysis, and preliminary computational modelling of tsunami resonance are discussed for various investigated sites on Savai'i and Upolu (Independent State of Samoa), and Ta'u (Manu'a Group, American Samoa). We show that a long-term geologic record of tsunamis exist on these islands. Further, we discuss the challenges encountered in detailing this record, as well as the challenges that remain in forming definitive interpretations. Ultimately, results from this project will contribute to enhancing our understanding of tsunami processes and their long-term risk in the Samoan Islands, and will contribute to forming a solid foundation for future studies to build on.