Abstract

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 moderate 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 slip, 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.

Highlights

  • The northeast coast of South Island, New Zealand, was ruptured by a large earthquake (Mw 7.8) on 13 November 2016 (UTC) which is widely known as the Kaikoura earthquake (Fig. 1)

  • As the 2016 tsunami was not large enough, we look at three near-field tide gauge stations of Kaikoura, Sumner, and Wellington to compare the performance of the source models

  • We studied the 13 November 2016 Kaikoura, New Zealand tsunami through waveform analysis and numerical simulations

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Summary

Introduction

The northeast coast of South Island, New Zealand, was ruptured by a large earthquake (Mw 7.8) on 13 November 2016 (UTC) which is widely known as the Kaikoura earthquake (Fig. 1). The earthquake was followed by a tsunami reaching a maximum runup height of around 7 m in the near field (Power et al 2017; Bradley et al 2017), the maximum zero-to-crest tide gauge height observed at the near-field station of Kaikoura was *2.6 m (Fig. 3). Possible Dual Earthquake–Landslide Source of the 13 November 2016 Kaikoura observations revealed evidence for rupture on various faults (Hamling et al 2017). We perform numerical simulations to shed light on the type of the tsunami source and to study tsunami propagation in the region

Data and Methods
Tsunami Waveforms
Tsunami Spectra
Wavelet Analysis
Tsunami Source
Regional Tsunami Propagation
Conclusions
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