HR: 17:15h
AN: NS24A-06    [Abstracts]
TI: High Resolution Seismic Reflection Survey Across a Segmentation Transfer Zone in the Ostler Fault Zone, South Island, New Zealand
AU: * Campbell, F M
EM: campbell@aug.ig.erdw.ethz.ch
AF: ETH Zürich, Applied and Environmental Geophysics, Institute of Geophysics, HPP, Schafmattstr.30, Zürich, 8093, Switzerland
AU: Kaiser, A
AF: ETH Zürich, Applied and Environmental Geophysics, Institute of Geophysics, HPP, Schafmattstr.30, Zürich, 8093, Switzerland
AU: Stratford, W
AF: Geologisk Institut, Kobenhavns Universitet, Oster Voldgade 10, Kobenhavn, 1350, Denmark
AU: Horstmeyer, H
AF: ETH Zürich, Applied and Environmental Geophysics, Institute of Geophysics, HPP, Schafmattstr.30, Zürich, 8093, Switzerland
AU: Finnemore, M
AF: Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
AU: Marescot, L
AF: ETH Zürich, Applied and Environmental Geophysics, Institute of Geophysics, HPP, Schafmattstr.30, Zürich, 8093, Switzerland
AU: Nobes, D
AF: Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
AU: Green, A
AF: ETH Zürich, Applied and Environmental Geophysics, Institute of Geophysics, HPP, Schafmattstr.30, Zürich, 8093, Switzerland
AB: The majority of the ~45 mm/yr of oblique convergence between the Pacific and Australian plates in the South Island of New Zealand is accommodated on the Alpine Fault. Further convergence is distributed onto structures east of the Alpine Fault. The Ostler Fault Zone is one of these structures, accommodating 1 - 2 mm/year of east- west compression. The fault consists of a series of predominantly west-dipping, highly segmented, surface rupturing thrust faults that transect Quaternary glacial outwash terraces in the Mackenzie Basin. This study focuses on the Benmore section of the fault zone, where folding and a series of small faults accommodate displacement in a transfer zone between two non-overlapping fault segments. Although fault traces have been extensively mapped at the surface and ground-penetrating radar data image steeply dipping faults at depths less than 5 metres, little is known of the structure at greater depths. We have conducted a high resolution seismic reflection survey to determine the structure of the fault, and associated deformation in the hanging wall, and to track lateral variations in these structures across the transfer zone. Twelve 1.2-km-long seismic lines were recorded perpendicular to the fault strike, covering approximately 1.6 km of fault length. Two additional tie lines were recorded parallel to strike. We used a 240 channel acquisition system with 3 and 6 m receiver and shot spacings, respectively. In addition, we recorded a 340-m-long ultra-high-resolution line with 0.5 m receiver and 1m shot spacing. Application of standard seismic reflection processing techniques to these high quality data sets reveals dipping sedimentary layering in both the hangingwall and the footwall down to 650 ms two way travel time, where a strong horizontal reflection occurs. Additional, weaker, horizontal reflections are recorded down to 1300 ms ttwt. Structures identified so far indicate that compression in the hanging wall of the fault is accommodated by both folding and subsidiary faulting, varying laterally across the transfer zone. More sophisticated processing techniques are being applied in an attempt to image steeper dipping structures.
DE: 0935 Seismic methods (3025, 7294)
DE: 8010 Fractures and faults
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting