Seismic site characterization - Alpine Fault drilling project

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The Alpine Fault (South Island, New Zealand) is one of the largest active fault zones on earth. It ruptures every 200-400 years in a magnitude ~7.9 earthquake, and is thought to have last ruptured in AD 1717, which implies a significant geohazard potential. In addition to its seismic hazard, the Alpine Fault constitutes an internationally significant natural laboratory for research into how active plate-bounding continental faults work and, in particular, the nature of earthquake generation. The "Deep Fault Drilling Project - Alpine Fault (DFDP-AF) proposes to drill, sample, and monitor the Alpine Fault at depth, to take advantage of excellent surface exposures and the relatively shallow depths of geological transitions, and hence to better understand fundamental processes of rock deformation, seismogenesis (earthquake initiation and rupture), and earthquake deformation. Key to the viability of this planned drilling operation is an improved knowledge of the detailed geometry and structure of the Alpine Fault, especially at the depths which the proposed drilling operation might target. We propose to process existing and newly acquired active and passive seismic data sets to determine the geometry and structure of the Alpine Fault system. The principal results will be high-resolution images of the fault zone structure at depth, which will serve primarily as a seismic site characterization study for the detailed selection of the DFDP-AF drill site as well as for a better understanding of the tectonic and geodynamic setting. Subsequently the results can also be used by other researchers for reliable assessment of the related geohazard, providing an important basis for most of the associated DFDP-AF research groups.