New Zealand Journal of Geology and Geophysics abstracts

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Neotectonics of the offshore Cape Egmont Fault Zone, Taranaki Basin, New Zealand

SCOTT D. NODDER

New Zealand Oceanographic Institute
National Institute of Water & Atmospheric Research Ltd
P.O.Box l4 901, Kilbirnie
Wellington, New Zealand

Abstract The Cape Egmont Fault Zone (CEFZ) is a major structural boundary within the predominantly offshore Taranaki Basin. The northeast-southwest-striking principal fault within this zone, the Cape Egmont Fault (CEF), represents the westernmost zone of active deformation associated with the Hikurangi subduction system, and is characterised by normal separation and pronounced surface expression across the Taranaki continental shelf. It has a 53 km long, 1-5 m high seafloor scarp, located 6 km to the east of the Maui-A production platform, and comprises four segments, each characterised by differences in fault geometry and behaviour. Average slip rates on the CEF for the last 225 000 years range from 0 to 0.8 mm/yr, suggesting concomitant extension rates of 0.1-1.8 mm/yr that are comparable with the deformation rates calculated for onshore active faults in the Taranaki-Wanganui region. The presence of a seafloor scarp and historic seismicity associated with the CEFZ are considered to be indicative of the recently active nature of the CEF. Analyses of high-resolution seismic reflection profiles and piston core samples suggest that the most recent movement on the CEF was at least post-10-11 ka ago. During the late Pliocene-Quaternary, it is unlikely that the CEFZ has accommodated significant amounts of strike-slip, as proposed by previous workers. Movement over the last 2-3 Ma is inferred to hav >een predominantly normal, possibly with an element of dextral oblique-slip.

Keywords Taranaki Basin; Cape Egmont Fault; fault segmentation; slip rates; normal faulting; seafloor scarp; Quaternary deformation

Received 2 November 1992; published 25 June 1993
New Zealand Journal of Geology & Geophysics, 1991, Vol. 36: 167—184
0028Ð8306/06/3602—0167 ©The Royal Society of New Zealand 1991

PDF file of entire paper: medium quality (5959K); (scanned from paper original: notes about this process). Digitisation of this article from the printed journal was kindly facilitated by the Geological Society of New Zealand

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