The Alpine Fault in New Zealand is one of only a few active transform fault boundaries worldwide that offsets continental terrains. Although paleoseismological data suggest that large earthquakes have struck the Fault in the past, it has been quiescent for at least the past 200 years. We have acquired five high-resolution seismic reflection profiles across the Alpine Fault a little to the north of its intersection with the Hope Fault. Slip-rates on the Alpine Fault appear to decrease by ~50% in crossing the Hope Fault from south to north, and at our study site the faulting is distinguished by step-overs and/or multiple strands. Accordingly, the goals of our seismic investigation are to define the structure of the Alpine Fault in the top few hundred metres of the subsurface with emphasis on defining its step-over or multi-strand character at the study site. Our seismic images contain evidence for significant changes in geometry across one major fault strand and an astonishingly abrupt transition from a highly reflective region to a non-reflective region across another major strand.


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