Predecessors to the 2009 South Pacific tsunami in the Wallis and Futuna archipelago

Multi-proxy studies of trench sediments from Futuna island, in the Wallis and Futuna archipelago, have produced a record of two palaeotsunamis dated to around 1860-2000 BP and c. 470 BP. One of the most useful proxies in this study has been the archaeological data associated with occupations that immediately underlie the deposits associated with both palaeotsunamis. The reworking of the archaeological material into the palaeotsunami deposits and the additional chronological control provided by artefacts have added value to interpretations based upon more conventional earth science proxies. The identification of tsunamigenic sources for these events is tentative and based upon known potential sources. Based upon a comparison between the effects of the 2009 South Pacific tsunami and those recorded in the trenches, Event 1(1860-2000 BP) appears most likely to be associated with a large tsunami sourced from the Tonga-Kermadec Trench region. There are only rare contemporaneous events reported from around the region, although this appears to be largely due to a lack of similar research as opposed to a lack of evidence. Event 2 (c. 470 BP) is markedly larger than Event 1, with sedimentary evidence indicating significant inland inundation and runup around the entire island. There are several lines of evidence for a contemporaneous event in the South Pacific around 470 BP, although much of this needs further verification. Determining a source for this event is problematic because it must take in to account the regional signal and the significant impacts recorded on Futuna. We propose that the source for this younger event was either a larger Tonga-Kermadec Trench-related earthquake or the Kuwae caldera collapse in 1452/1453 AD. We recognise that as further research is carried out in the Pacific we will greatly improve our abilities to identify past sources and the magnitude and frequency of past events from these areas. This can only serve to improve our understanding of the regional risk from tsunamis. (C) 2010 Elsevier B.V. All rights reserved.