Assessing the contribution of off‐fault deformation to slip‐rate estimates within the Taupo Rift,New Zealand,using 3‐D ground‐penetrating radar surveying and trenching |
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| Authors: | Alastair Fergus McClymont Pilar Villamor Alan G Green |
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| Institution: | 1. Department of Geoscience, University of Calgary, 2500 University Drive NW, T2N1N4, Calgary, AB, Canada;2. GNS Science, Lower Hutt, New Zealand;3. Institute of Geophysics, Swiss Federal Institute of Technology, Zurich, Switzerland |
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| Abstract: | We demonstrate that conventional palaeoseismic trenching and mapping techniques that do not account for the effects of off‐fault deformation can significantly underestimate a fault’s slip rate. Using combined interpretations of 3‐D ground‐penetrating radar (GPR) and palaeoseismic trench data, we show that drag folding and hangingwall and footwall horizontal‐axis rotations have accommodated up to 41% of total extension across a normal fault within the Taupo Rift, New Zealand, over the past 24.6 ± 1.0 cal. ka BP. Our results may explain why geologically determined fault‐slip rates for the central and southern Taupo Rift are anomalously low when compared with geodetic estimates. We suggest that a combination of GPR surveying and palaeoseismic trenching may help resolve differences between geodetically and geologically determined strain rates observed across active extensional regimes worldwide. |
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