Possible dual earthquake-landslide source of the 13 November 2016 Kaikoura, New Zealand tsunami

Abstract

Copyright © The Author(s) 2017. A complicated earthquake (Mw 7.8) in terms of rupture mechanism occurred in the NE coast of South Island, New Zealand on 13 November 2016 (UTC) in a complex tectonic setting comprising a transition strike-slip zone between two subduction zones. The earthquake generated a small tsunami with zero-to-crest amplitude of 257 cm at the near-field tide gauge station of Kaikoura. Spectral analysis of the tsunami observations showed dual peaks at 3.6–5.7 and 5.7–56 min, which we attribute to the potential landslide and earthquake sources of the tsunami, respectively. Tsunami simulations showed that a source model with slip on an offshore plate-interface fault reproduces the near-field tsunami observation in terms of amplitude but fails in terms of tsunami period. On the other hand, a source model without offshore slip fails to reproduce the first peak, but the later phases are reproduced well in terms of both amplitude and period. It can be inferred that an offshore source is necessary to be involved, but it needs to be smaller in size than the plate-interface, which most likely points to a confined submarine landslide source; consistent with the dual-peak tsunami spectrum. We estimated the dimension of the potential submarine landslide at 8–10 km.