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Caroline Dorn, ETH Zürich (Switzerland)
Fiona Campbell, ETH Zürich (Switzerland)
Fiona Kaiser, ETH Zürich (Switzerland)
Heinrich Horstmeyer, ETH Zürich (Switzerland)
Alan Green, ETH Zürich (Switzerland)
Stefan Carpentier, ETH Zürich (Switzerland)
Michael Finnemore, University of Canterbury (New Zealand)
David Nobes, University of Canterbury (New Zealand)
Jocelyn Campbell, University of Canterbury (New Zealand)
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The Springfield Fault System is part of a network of splays and overlapping faults that are generally hidden beneath Quaternary sediments of the Canterbury Plains on the South Island of New Zealand. These faults accommodate an important component of motion between the Pacific and Australian tectonic plates. Limited exposures of the faults suggest that they are mostly west facing thrusts that have tilted (by 30° to 60°) and displaced Tertiary limestones and volcanics and Jurassic Torlesse basement. In an attempt to map faults of the Springfield Fault System, we have acquired high-resolution seismic reflection and ground-penetrating radar (GPR) data along four nearly parallel lines that range in length from 3 to 18 km. The seismic data were acquired using small explosive and hammer sources at 10 m intervals and a receiver spread comprising two hundred and forty 30-Hz geophones at 5 m intervals, yielding nominal 60-fold data with a CMP spacing of 2.5 m. In contrast the GPR data were recorded using 50 MHz antennas separated by 2 m. Preliminary processing of the seismic data reveal prominent reflections from the dipping geological strata at 80 m and greater depths, which are interrupted by at least two major fault strands. We hope that the processed GPR data will be able to determine whether or not the faults have offset the Quaternary sediments. A major goal is to improve our understanding of active tectonism and seismic hazard in this moderately populated region of New Zealand.
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