Hobart

Seminar Abstract

Friday 20 November 2009, 11.30am (Tas time)
CSIRO Auditorium, Hobart

Geoffroy Lamarche
Principal Scientist Marine Geology and Geophysics
National Institute of Water and Atmospheric (NIWA) Research Ltd
Wellington, New Zealand

Characterisation and quantification of seafloor geology and natural hazard in Cook Strait, New Zealand

Cook Strait between New Zealand's north and south islands is an area of strategic public and economic interest. Occurrence of numerous major tectonic fault, deep canyons carving into the continental shelf and multiple landslides scars along the steep continental slope all concur to indicate high submarine geological hazard in the immediate vicinity of the country capital city. The diversity of biota and faunas in this highly dynamic oceanographic environment also stress the importance of improving our understanding of the inter-relationships between biodiversity and geology. Geophysical surveys in the Cook Strait have resulted in a huge amount of multibeam bathymetry and backscatter, multichannel and high resolution seismic reflection data. Two research projects have benefited hugely from the acquisition and interpretation of these data:

1) The identification and characterisation of active faults and earthquake sources. High resolution seismic data provide a mean to identify active faults at, and beneath the seafloor, estimate their rate of activity and evaluate their potential as earthquake sources. We were able to derive the first paleoearthquake records from submarine faults in New Zealand, with six paleoearthquake ruptures inferred since 12 000 years ago along one single fault segment.

2) The quantitative characterization of seafloor geological features using advanced processing of multibeam backscatter. The Backscatter Strength (BS) provides quantitative, repeatable information on the acoustic characteristics of the seafloor, and has enabled us to characterize geological and topographic features otherwise not recognized with the same level of details using conventional surveying methods. The variation of the BS as a function of the acoustic waves incidence on the seafloor is a good indicator of the sediment grain size, and represents a first-order proxy of the large-scale geology.

Seminar Recording

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Clothilde Langlais, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5399
Natalie Kelly, (Biology/Modelling seminars) CSIRO Marine and Atmospheric Research 0438 452 483
Jillian Enraght-Moony, (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5320
Communications Manager, Antarctic Climate and Ecosystems CRC (03) 6226 2265
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 8/12/09