Geometries and slip of historical surface-rupturing earthquakes in New Zealand and their application to seismic hazard analysis

Abstract

This project was conceived prior to the 2016 Kaikōura Earthquake after recognising that many of New Zealand’s historical earthquakes produced displacement on interconnected networks of active faults (e.g., 1987 Edgecumbe and 2010 Darfield earthquakes). The Kaikōura Earthquake ruptured at least 17 separate faults and reminded the global earthquake community of the potential for large earthquakes to break more than one fault.

It is clear from the Kaikōura Earthquake that such ruptures can be complicated, however, questions remain about how frequently they occur, what controls these multiple-fault earthquakes and whether we should expect similarly complex faulting patterns in future earthquakes? To address these questions we have reanalysed the literature and digital elevation models of the ground-surface for eight moderate to great historical earthquakes (magnitudes 6.4-8.2) in New Zealand since 1840. Of these earthquakes, at least five involved three or more faults (Wairarapa 1855, Hawkes Bay 1931, Edgecumbe 1987, Darfield 2010 and Kaikōura 2016 earthquakes).

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