North Island subduction objective
Objective Leader: Dr. Stephen Bannister
The Pacific plate has its sediment scraped from it, as it converges with and sinks beneath the eastern North Island. This is called a subduction zone, and its faulted interface is called the subduction thrust. The largest recorded earthquakes on Earth occur on subduction thrust faults around the Pacific, but it is unknown if such earthquakes will occur beneath the North Island. In this objective, we image the structure beneath the North Island using natural and man-made seismic waves. We also carry out geological studies to establish if there is evidence in coastal regions for previous subduction zone earthquakes. Images of the deformed sedimentary basins are of use in petroleum exploration, and our data is passed on to the petroleum industry. Our interpretations of the likelihood and effects of future subduction zone earthquakes are necessary for informed hazard planning in the region; our research results will be communicated via talks, workshops, communication with relevant authorities, and the GNS hazards research program.
We currently have three tasks within the objective:
1 Central North Island Passive Seismic experiment - CNIPSE (leader Dr. Martin Reyners): A large dataset of natural earthquakes (mainly recorded in 2001-2) is used to image the crust and upper mantle.
Download a poster of recent tomographic results:
CNIPSE poster.pdf (996.72 kB)
Download a poster describing active processes on the plate interface beneath the North Island:
peachhorne_poster.pdf (541.77 kB)
2 North Island Geophysical Transect - NIGHT (leader Dr. Stuart Henrys): A companion study to CNIPSE used artificially generated seismic waves to illuminate the structure of the offshore basins and the crust beneath eastern North Island.
3 Subduction earthquake geology (leader Dr. Ursula Cochran): Sediment cores are taken from coastal environments near Hawke Bay and analysed to determine if there is a record of ancient catastrophic events.
Selected publications
Darby, D.J.; Beavan, R.J. 2001: Evidence from GPS measurements for contemporary interplate coupling on the southern Hikurangi subduction thrust and for partitioning of strain in the upper plate. Journal of geophysical research. Solid earth 106(B12): 30881-30891.
McGinty, P.; Darby, D.; Haines, J. 2001: Earthquake triggering in the Hawke's Bay, New Zealand, region from 1931 to 1934 as inferred from elastic dislocation and static stress modeling. Journal of Geophysical Research, B, Solid Earth and Planets 106: 26,593-26,604.
Reyners,M.E., 2000. Quantifying the hazard of large subduction thrust earthquakes in Hawke's Bay. Bull of New Zealand National Society for Earthquake Engineering., 33(4), 477-483.
Henrys,S.A., Reyners,M., Bibby,H., 2003. Exploring the plate boundary structure of New Zealand. EOS Transactions of the American Geophysical Union, v84 (289), p294-295.
Nicol, A.; Van Dissen, R.J.; Vella, P.; Alloway, B.V.; Melhuish, A. 2002: Growth of contractional structures during the last 10 m.y. at the southern end of the emergent Hikurangi forearc basin, New Zealand. New Zealand journal of geology and geophysics 45(3): 365-385.
Eberhart-Phillips, D., Reyners, M., Chadwick, M. & Chiu, J-M., 2005. Crustal heterogeneity and subduction processes: 3-D Vp, Vp/Vs and Q in the southern North Island, New Zealand. Geophys. J. International, 162, 270-288.
Reyners, M., Eberhart-Phillips, D., Stuart, G. & Nishimura, Y., 2006. Imaging subduction from the trench to 300 km depth beneath the central North Island, New Zealand, with Vp and Vp/Vs. Geophys. J. International, 165, 565-583.
Follow the links above to individual research project pages.