Three-dimensional tomographic imaging of the Taranaki volcanoes, New Zealand

Sherburn, S. and White, R. S. and Chadwick, M (2006) Three-dimensional tomographic imaging of the Taranaki volcanoes, New Zealand. Geophysical Journal International, 166. 957–969; doi:10.1111/j.1365-246x.2006.03040.x. DOI https://doi.org/10.1111/j.1365-246X.2006.03040.x

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Abstract

3-D models of the P-wave velocity (Vp), the ratio of P- to S-wave velocity (Vp/Vs), and the P-wave quality factor (Qp) are determined for the crust in Taranaki, New Zealand, using local tomography and data from a dense network (average spacing 5 km) of 68 three-component, broad-band seismographs. Vp and Vp/Vs models were determined by jointly inverting P traveltimes and S–P traveltime intervals, and a Qp model by inverting t* (t/Qp) observations derived from modelling the velocity amplitude spectrum of P wave arrivals. An approximately 5 km diameter region of high Vp and low Vp/Vs beneath the Taranaki volcanoes extends from the surface to a depth of about 10 km and images the roots of the volcanoes formed by successive magmatic intrusions. At Mt Taranaki this will probably be the path through which future magma intrusions will reach the surface. We are unable to image any magma storage within the upper 16 km of the crust as the volumes involved are probably smaller than the 5 km resolution of our models. The volcanoes sit in the Taranaki basin, a large sedimentary basin characterized by low Vp (c. 4 km s−1) and high Vp/Vs (≥1.9), attributed to unconsolidated, water-saturated sediments, and these are underlain by basement rocks with Vp≥ 5 km s−1 and Vp/Vs≤ 1.7 . There is a c. 20 per cent contrast in Vp across the Taranaki fault at the eastern boundary of the Taranaki basin, and a small, shallow, high Vp/Vs (≥2.0) anomaly above the seismically active Cape Egmont Fault Zone, west of the Taranaki volcanoes. Although the Qp model is of significantly lower resolution than the Vp and Vp/Vs models, it shows a low Qp anomaly (c. 100) between 4 and 10 km depth that corresponds to the deepest onshore part of the Taranaki basin.

Item Type:	Article
Uncontrolled Keywords:	2006 AREP IA49 IA51 2006 P
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title:	Geophysical Journal International
Volume:	166
Page Range:	957–969; doi:10.1111/j.1365-246x.2006.03040.x
Identification Number:	https://doi.org/10.1111/j.1365-246X.2006.03040.x
Depositing User:	Sarah Humbert
Date Deposited:	16 Feb 2009 13:03
Last Modified:	23 Jul 2013 10:08
URI:	http://eprints.esc.cam.ac.uk/id/eprint/684

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