[J02-3] Recent large earthquakes III

[J02-3-01] Shattering a plate boundary: Complex multi-fault rupture during the 2016 Mw 7.8 Kaikoura earthquake, New Zealand

^○Ian Hamling¹, Sigrun Hreinsdottir¹, Stephen Bannister¹, Eric Fielding², Bill Fry¹, Caroline Holden¹, Ana Kaiser¹, Nicola Litchfield¹, Christof Mueller¹, Laura Wallace^1,3, Tim Wright⁴ (1.GNS Science, Lower Hutt, New Zealand, 2.Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, 3.University of Texas Institute for Geophysics (UTIG), Austin, Texas, USA, 4.University of Leeds, Leeds, UK)

invited

On 14th November 2016, the northeastern South Island of New Zealand was struck by a major Mw 7.8 earthquake. The earthquake was the most powerful experienced in the region in more than 150 years. Shaking felt across the whole of New Zealand with widespread damage across much of the northern South Island and in New Zealand's capital city, Wellington. The earthquake straddled two distinct seismotectonic domains, breaking multiple faults in the predominantly strike-slip Marlborough Fault System and the contractional North Canterbury fault zones. Aftershocks continue to follow a broad NE-SW trend proximal to the Humps and Hundalee faults in the North Cantebury fault zone before stepping north, approximately following the Jordan Thrust and Kekerengu faults. Field observations, in conjunction with InSAR, GPS, and seismology reveal this to be one of the most complex earthquakes ever recorded. The rupture propagated northward for more than 170 km along both mapped and unmapped faults, before continuing offshore at its northeastern extent. The earthquake also generated a tsunami which was detected at four tide gauges along the east coast of the both the North and South Islands. Simple travel time inversion places the source of the tsunami in the coastal area ranging from just south of Kaikoura northwards to Cape Campbell. Geodetic and field observations reveal surface ruptures along at least 12 major crustal faults, extensive uplift along much of the coastline and widespread anelastic deformation including the ~8 m uplift of a fault-bounded block. While most of the deformation can be explained by crustal faulting alone, global moment tensors show a larger thrust component suggesting that the southern end of the Hikurangi may have also slipped. This complex earthquake defies many conventional assumptions about the degree to which earthquake ruptures are controlled by fault segmentation, and should motivate re-thinking of these issues in seismic hazard models.