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Imaging of the Shallow Alpine Fault Zone (New Zealand) Using 2D and Pseudo 3D Seismic Reflection DataNormal access

Authors: A.E. Kaiser, H. Horstmeyer, A.G. Green, F. Campbell, R.M. Langridge and A.F. McClymont
Event name: Near Surface 2010 - 16th EAGE European Meeting of Environmental and Engineering Geophysics
Session: High Resolution Seismic & Archeological Geophysical Investigations
Publication date: 06 September 2010
DOI: 10.3997/2214-4609.20144824
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.6Mb )
Price: € 20

The Alpine Fault Zone in New Zealand's South Island is part of the boundary between the Australian and Pacific tectonic plates. We use ultra-high-resolution 2D and high-resolution pseudo-3D seismic reflection imaging to investigate the structure of the fault and adjacent subsurface in a northern part of the Island. Employing acquisition schemes that minimise field effort while yielding high-resolution data together with fine-tuned processing strategies, we derive high-quality images of the shallow subsurface down to about 200 m depth. Gravels with a maximum thickness of ~50 m are seen on the two sides of the fault. On the hangwall side, these gravels overlie up to ~90 m of glaciolacustrine sediments.The basement underneath is interpreted to be an erosional surface that has been folded and faulted. The principal strand of the Alpine Fault Zone is shown to have a dip of 75° - 80° from the surface to the basement at ~60 m depth. The dip at greater depths is not well constrained, but is likely to range from 50° - 80°. The ~25 m apparent vertical offset of the basement yields an average dip-slip rate of 2.0 ± 1 mm/yr.

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