Preprints
https://doi.org/10.5194/nhess-2022-157
https://doi.org/10.5194/nhess-2022-157
 
07 Jun 2022
07 Jun 2022
Status: this preprint is currently under review for the journal NHESS.

Potential tsunami hazard of the southern Vanuatu Subduction Zone: tectonics, case study of the Matthew Island tsunami of 10 February 2021 and implication in regional hazard assessment

Jean Roger1, Bernard Pelletier2, Aditya Gusman1, William Power1, Xiaoming Wang1, David Burbidge1, and Maxime Duphil3,4 Jean Roger et al.
  • 1GNS Sciences, 1 Fairway Drive, Lower Hutt 5010, New Zealand
  • 2GEOAZUR, Institut de Recherche pour le Développement, 101, Promenade Roger Laroque, BP A5 98848 Nouméa CEDEX, New Caledonia
  • 3ENTROPIE, Institut de Recherche pour le Développement, 101, Promenade Roger Laroque, BP A5 98848 Nouméa CEDEX, New Caledonia
  • 4École Doctorale no 129 Sciences de l'Environnement, UPMC Sorbonne Université, 4, Place Jussieu, 75005, Paris CEDEX, France

Abstract. The Vanuatu subduction zone (VSZ) is known to be seismically very active, releasing a significant energy resulting of the quick convergence rate between the Australian and Pacific tectonic plates. That is not the case on its southernmost part south of latitude 22.5° S and east of longitude 170° E which is neither known as being highly tectonically active nor having produced large tsunamis over the past 150 years, and by the way, has not been much studied. On the 11th of February 2021 (10 February UTC), a magnitude Mw 7.7 earthquake triggered a tsunami warning in New Caledonia and Vanuatu twenty minutes after midnight (local time). With an epicentre located close to the volcanic islands of Matthew and Hunter, this shallow reverse-faulting rupture (< 30 km depth) was able to disturb the seabed and produce a tsunami. In fact, it was confirmed 45 min later by the coastal gauges of the Loyalty and the south Vanuatu islands which recorded the first tsunami waves. Showing an overall recorded amplitude of less than 1 m with a maximum of ~1.5 m in Lenakel, (Tanna, Vanuatu), it has been recorded on most coastal gauges and DART stations of the southwest Pacific Region as far as Tasmania in the South and Tuvalu in the North respectively at distances of ~3000 and ~1800 km from the epicentre. In this study, the tsunamigenic potential of the southernmost part of the VSZ and the implications in terms of regional hazard assessment are discussed through (1) the presentation of the complex tectonic settings of this “transition zone” between the Solomon-Vanuatu and the Tonga-Kermadec Trenches; (2) the case study of the 10 February 2021 tsunami at a southwest Pacific regional scale using three different tsunami generation scenarios computed with COMCOT modelling code on a set of 48 nested bathymetric grids; and (3) the simulation of a plausible Mw 8.2 scenario encompassing the active part of this “transition zone”. In fact, the validation of the Mw 7.7 parameters for tsunami modelling provides keys to further assess the hazard from potential tsunami triggered by higher magnitude earthquakes in this region. Finally, it helps to highlight the significant role played by the numerous submarine features in the region, the Norfolk Ridge being the most important acting like a waveguide toward the north and the south.

Jean Roger et al.

Status: open (until 19 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-157', Anonymous Referee #1, 28 Jun 2022 reply

Jean Roger et al.

Jean Roger et al.

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Short summary
On 10 February 2021 a magnitude 7.7 earthquake occurring at the southernmost part of the Vanuatu subduction zone triggered a regional tsunami that was recorded on many coastal gauges and DART stations of the southwest Pacific region. Beginning with a review of the tectonic setup and its implication in terms of tsunami generation in the region, this study aims to show our ability to reproduce a small tsunami with different types of rupture model, and to discuss a larger magnitude 8.2 scenario.
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