Continental drilling through the shallow Alpine fault, New Zealand

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Gouge from seismogenic fault zones provide key information associated with earthquake mechanisms and were/are the focus of various ICDP initiatives. Most recently, the Alpine Fault, New Zealand, was subject to a pre-proposal to ICDP, which was followed by a workshop in March 2009, so that we now propose a low-budget pilot drill hole (300 m depth) to set the stage for future deep ICDP drilling through the fault in early 2011. The hole will be adjacent to a 300-m hole already funded by UK and NZ and would provide (i) extra core material for mineralogical-petrological studies of the fault zone and wall rock composition, (ii) whole round cores for geotechnical testing under seismogenic conditions (up to 200 MPa normal stress and 200°C), and (iii) an option for future long-term instrumentation and in situ monitoring. The approach will help to assess what has to be expected in the deep ICDP hole, whether the Alpine Fault gouge material is capable of generating large magnitude earthquakes, and what processes govern fault zone mineralogical alteration. In short, this low-cost drill hole will maximise the pilot study outcome and provide German researchers immediate access to this challenging ICDP deep drilling effort.