Crustal and upper mantle structure of the northwestern North Island, New Zealand, from seismic refraction data |
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Authors: | Tim Stern E. G. C. Smith F. J. Davey K. J. Muirhead |
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Affiliation: | Geophysics Division, Department of Scientific and Industrial Research, PO Box 1320, Wellington, New Zealand;Research School of Earth Sciences, Australian National University, Canberra, Australia |
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Abstract: | The crustal and upper mantle structure of the northwestern North Island of New Zealand is derived from the results of a seismic refraction experiment; shots were fired at the ends and middle of a 575 km-long line extending from Lake Taupo to Cape Reinga. The principal finding from the experiment is that the crust is 25 ± 2 km thick, and is underlain by what is interpreted to be an upper mantle of seismic velocity 7.6 ± 0.1 km s−1, that increases to 7.9 km s−1 at a depth of about 45 km. Crustal seismic velocities vary between 5.3 and 6.36 km s−1 with an average value of 6.04 km s−1. There are close geophysical and geological similarities between the north-western North Island of New Zealand and the Basin and Range province of the western United States. In particular, the conditions of low upper-mantle seismic velocities, thin crust with respect to surface elevation, and high heat-flow (70–100 mW m−2) observed in these two areas can be ascribed to their respective positions behind an active convergent margin for about the past 20 Myr. |
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Keywords: | seismic refraction crust–upper mantle structure back-arc volcanism gravity edge-effect New Zealand |
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