Observational and theoretical aspects of tsunami sedimentation
This dissertation presents the detailed results of investigations into the coastal geomorphological effects and sedimentation processes associated with a recent large tsunami event which took place on the 12th December 1992 in Flores, Indonesia, and the stratigraphical and sedimentological study of a widespread sand layer preserved in coastal sedimentary sequences along the eastern coast of Scotland representing a low-frequency, high-energy marine event, which took place at circa 7,000 radiocarbon years B.P. With modern alalogues, established in this dissertation, of both tsunami and storm surge sedimentary characteristics and sedimentation processes as the key, together with high-resolution sedimentological evidence obtained from the circa 7,000 radiocarbon years B. P. event, competing hypotheses of the likely causes of the marine flooding by either a tsunami or storm surge event are tested. It is concluded that the circa 7,000 B. P. marine flooding event was a tsunami, believed to have been generated by one of the world's largest submarine landslides in the Norwegian Sea - the Second Storegga Slide. The particle size composition of tsunami sediments is found to vary from well sorted to poorly sorted and is controlled by both the characteristics of the source sedement (local coastal sediments) and sedimentation processes associated with tsunami inundation. Tsunami sediments deposited on land are believed to form continuous and discontinuous sedimentary sheets ascending up to levels distinctively higher than contemporary sea levels and to contain a general landward-fining trend and multiple sets of grading (fining-upward) sequences, reflecting spatial changes in particle size composition. A conceptual model of coastal tsunami sedimentation is established including processes of seaward and landward sediment movements, episodic rapid deposition, sediment accumulation and erosion.