New Zealand Journal of Geology and Geophysics abstracts

---

Imaging the Wairarapa Fault at Tauwharenikau using magnetotelluric sounding

Olaf Ingo von Borstel

School of Earth Sciences
Victoria University of Wellington
P.O. Box 600
Wellington, New Zealand*

Malcolm Ingham

School of Chemical & Physical Sciences
Victoria University of Wellington

*Present address: Astrophysical Institute and University Observatory, Friedrich Schiller University Jena, Schillergaesschen 2, 07745 Jena, Germany.

Abstract  To test the ability of closely spaced magnetotelluric data to provide high resolution images of fault structures, measurements have been made across the Wairarapa Fault at Tauwharenikau, southern North Island, New Zealand. 2D inversion and modelling of the TM-mode data from 11 sites on a 1.5 km long transect show the transition from conductive Tertiary sediments southeast of the fault zone to resistive greywacke to the northwest, and also illustrate some of the difficulties in interpretation that can arise. The existence of dual fault traces separated by some 100 m allows for two possible interpretations of the electrical structure: (1) that the southeastern fault trace represents the main trace of the Wairarapa Fault and that low resistivity to the northwest is the result of fluid percolation into fractured rock between the fault traces; or (2) that the northwestern fault trace marks the actual contact between Tertiary sediments and greywacke. In this case, the near-surface dip of the fault is constrained to be c. 80° to the northwest.

Keywords   magnetotelluric sounding; Wairarapa Fault; New Zealand

G03014; Received 12 June 2003; accepted 8 December 2003; Online publication date 20 May 2004
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47: 281–286
0028–8306/04/4702–0281 © The Royal Society of New Zealand 2004

PDF file of entire paper: Print-quality (420K) | screen-quality (243K)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page