Imaging the Hikurangi subduction zone, New Zealand, using teleseismic receiver functions: crustal fluids above the forearc mantle wedge |
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Authors: | S Bannister M Reyners G Stuart M Savage |
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Institution: | GNS Science, PO Box 30368,;Lower Hutt 6315, New Zealand. E-mail: School of Earth and Environment, University of Leeds, Leeds, UK;Victoria University of Wellington, Wellington, New Zealand |
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Abstract: | We image the Hikurangi subduction zone using receiver functions derived from teleseismic earthquakes. Migrated receiver functions show a northwest dipping low shear wave feature down to 60 km depth, which we associate with the crust of the subducted Pacific Plate. Receiver functions (RF) at several stations also show a pair of negative and positive polarity phases with associated conversion depths of ∼20–26 km, where the subducted Pacific Plate is at a depth of ∼40–50 km beneath the overlying Australian Plate. RF inversion solutions model these phases with a thin low S -wave velocity zone less than 4 km thick, and an S -wave velocity contrast of more than ∼0.5 km s−1 with the overlying crust. We interpret this phase pair as representing fluids near the base of the lower crust of the Australian Plate, directly overlying the forearc mantle wedge. |
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Keywords: | crustal structure low-velocity layer plate boundary seismic array seismic velocities waveform analysis |
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