Two regions of seafloor deformation generated the tsunami for the 13 November 2016, Kaikoura, New Zealand earthquake

• Published in: Geophysical research letters 2017-07, Vol.44 (13), p.6597-6606
• Main Authors: Bai, Yefei, Lay, Thorne, Cheung, Kwok Fai, Ye, Lingling
• Format: Article
• Language: English
• Subjects: Body waves; Coastal environments; Deformation; Earthquake; Earthquakes; Fault lines; Faults; Gauges; Geological faults; Harbors; Hikurangi subduction zone; Islands; Iterative methods; Measuring instruments; Modelling; Ocean floor; Offshore; Regions; Rupture; Rupturing; Seismic activity; Slip; Tide gauges; Tides; Trenches (pipelines); Tsunami; Tsunamis; Uplift; Water levels
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2017GL073717

The 13 November 2016 Kaikoura, New Zealand, Mw 7.8 earthquake ruptured multiple crustal faults in the transpressional Marlborough and North Canterbury tectonic domains of northeastern South Island. The Hikurangi trench and underthrust Pacific slab terminate in the region south of Kaikoura, as the subdution zone transitions to the Alpine fault strike‐slip regime. It is difficult to establish whether any coseismic slip occurred on the megathrust from on‐land observations. The rupture generated a tsunami well recorded at tide gauges along the eastern coasts and in Chatham Islands, including a ~4 m crest‐to‐trough signal at Kaikoura where coastal uplift was about 1 m, and at multiple gauges in Wellington Harbor. Iterative modeling of teleseismic body waves and the regional water‐level recordings establishes that two regions of seafloor motion produced the tsunami, including an Mw ~7.6 rupture on the megathrust below Kaikoura and comparable size transpressional crustal faulting extending offshore near Cook Strait. Key Points The 2016 Kaikoura earthquake produced tsunami signals that indicate sizeable seafloor deformation in addition to onshore surface ruptures Iterative modeling of teleseismic P and SH waves and regional tide and wave gauge recordings indicates two regions of seafloor deformation Tsunami excitation involved oblique thrusting on the southern Hikurangi megathrust and offshore extension of transpressional faults