HR: 1330h
AN: OS22A-1149    [PDF]
TI: Dating Submarine Landslides: the July 17th 1998 Papua New Guinea Event
AU: * Tappin, D R
EM: drta@bgs.ac.uk
AF: David R Tappin, British Geological Survey Kingsley Dunham Centre Keyworth, Nottingham, NG12 5GG United Kingdom
AU: Okal, E
EM: emile@earth.northwestern.edu
AF: Emile Okal, Dept. of Geological Sciences Northwestern University, Evanston, IL 60208 United States
AB: Identification of a suitably located cohesive sedimentary slump offshore off the north coast of Papua New Guinea, mathematical modelling of which provided appropriate run-ups compared with onshore measurements, might have been expected to provide compelling evidence for the source of the registered tsunami in the context of an alternative hypothesis based on a shallow dipping thrust source. However, notwithstanding the evidence, alternative slump source mechanisms, as well as those attributed to a thrust fault, are still considered by some investigators as a likely alternative. In this context we present evidence on the dating of the slump by observational, acoustic and biological methods that supports the slump source of the tsunami. The observational data from Remote and Manned Submersibles shows that seabed features, such as fissures and fractured limestone, on the surface of the slump, to be more recently deformed than outside the slump area. Fluid expulsion from the seabed was only observed from the area of the slump mass. Additionally, the seabed chemosynthetic cold water faunas, such as mussels and tubeworms, as well as bacterial mats that are intimately associated with sulphide rich sediment, are much more common on the slump surface. Their presence is interpreted to indicate active expulsion of sulphide and methane rich pore fluids. T-phase data, from an unblocked hydrophone on Wake Island, in the context of the arrival time of the tsunami from eyewitness accounts and mathematical simulation, suggest that a slump source for the tsunami to be more likely than an earthquake.
DE: 3022 Marine sediments--processes and transport
DE: 3045 Seafloor morphology and bottom photography
DE: 3094 Instruments and techniques
DE: 4564 Tsunamis and storm surges
DE: 4804 Benthic processes/benthos
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting