The Past, Present and Future of Multi-Trace Reverse Faults in New Zealand

Intracontinental reverse faults in Otago and South Canterbury, Aotearoa-New Zealand, have complex surface morphologies. The Dunstan Fault and Fox Peak Fault are expressed at the surface by multiple parallel to sub-parallel fault traces. These traces can be hundreds of meters apart from each other and span a deformation zone up to 2-3km in width. We ask the following questions: Do all traces rupture together in each ground rupturing earthquake, or do they rupture independently? If traces rupture independently, is it random which trace ruptures in a given event, or is there a spatio-temporal pattern? What is the likelihood of a new trace rupturing in the next large earthquake? We use paleoseismic techniques to constrain the timings of past earthquakes on each trace. The results are compared to see if the same earthquake ruptured multiple traces. If we can tease out any spatio-temporal patterns, we may be able to answer the question: In a future ground rupturing earthquake, which trace/traces will rupture? The results have implications for fault zonation and fault displacement hazard analysis of intracontinental reverse faults in Aotearoa-New Zealand and beyond.