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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