The Taupe Volcanic Zone (TVZ) is a major Pliocene-Quaternary NNE-SSW orientated volcano-techonic complex, in central North Island, New Zealand. It is a region characterised by voluminous rhyolitic eruptions, high natural heat flow, intense shallow seismic activity and active NW-SE extension. The central portion of the TVZ is regarded as the most frequently active and productive silicic volcanic system on Earth, yet to date no direct evidence for the source for the magmatisim has been found. In February and December 2001, as part of the NIGHT (North Island GeopHysical Transect) experiment, a total of ten 500 kg land slots were fired into an NW-SE array that ran the width of central North Island, New Zealand. An additional passive array of broad-band and short-period instruments centred on the TVZ recorded local and teleseismic earthquakes for six and a half months. Forward and inverse modelling of this active and shallow (< 10 km) earthquake data shows low-velocity (2.0-3.5 km/s) volcanic sediments reaching a maximum thickness of 3 km beneath the central TVZ. Underlying these sediments to 16 km depth are velocities of 5.0-6.5 km/s, interpreted as quartzo-fieldspathic crust. East and west of the TVZ, these velocities are observed to depths of 30 and 23 km respectively. Beneath the TVZ, material with P-wave velocities of 6.9-7.3 km/s are observed to ~30 km depth and are interpreted as heavily intruded or underplated lower crust. Modelling of deep (> 40 km) earthquake events originating near the top of the subducting Pacific plate, reveals a low-velocity region (LVR) (Vp of 7.4-7.8 km/s) overlying a northwest dipping high-velocity structure that coincides with the Wadati-Benioff zone.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:603773 |
| Date | January 2004 |
| Creators | Harrison, A. J. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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