Preprints
https://doi.org/10.5194/nhess-2021-58
https://doi.org/10.5194/nhess-2021-58

  18 Mar 2021

18 Mar 2021

Review status: a revised version of this preprint was accepted for the journal NHESS and is expected to appear here in due course.

The Mw 7.5 Tadine (Maré, Loyalty Is.) earthquake and related tsunami of December 5, 2018: implications for tsunami hazard assessment in New Caledonia

Jean Roger1,a, Bernard Pelletier2, Maxime Duphil1, Jérôme Lefèvre1, Jérôme Aucan1, Pierre Lebellegard2, Bruce Thomas1,3, Céline Bachelier4, and David Varillon4 Jean Roger et al.
  • 1ENTROPIE, Institut de Recherche pour le Développement, 101, Promenade Roger Laroque, BP A5 98848 Nouméa CEDEX, New Caledonia
  • 2GEOAZUR, Institut de Recherche pour le Développement, 101, Promenade Roger Laroque, BP A5 98848 Nouméa CEDEX, New Caledonia
  • 3LISAH, Univ Montpellier, INRAE, IRD, Institut Agro, Montpellier, France
  • 4IMAGO, Institut de Recherche pour le Développement, 101, Promenade Roger Laroque, BP A5 98848 Nouméa CEDEX, New Caledonia
  • anow at: GNS Sciences, 1 Fairway Drive, Lower Hutt 5010, New Zealand

Abstract. On the 5th of December 2018, a magnitude Mw 7.5 earthquake occurred southeast of Maré, an island of the Loyalty Archipelago, New Caledonia. This earthquake is located at the junction between the plunging Loyalty ridge and the southernmost Vanuatu arc, in a tectonically very active area regularly subjected to strong seismic crises and events higher than magnitude 7 and up to 8. Widely felt in New Caledonia it has been immediately followed by a tsunami warning, confirmed shortly after by a first wave arrival at the Loyalty Islands tide gauges (Maré and Lifou), then along the east coast of Grande Terre of New Caledonia and in several islands of the Vanuatu Archipelago. Seafloor initial deformation linked to tsunami generation has been modeled with MOST numerical code using earthquake parameters available from seismic observatories. Then the wave propagation has been modeled using SCHISM, another modelling code solving the shallow water equations on an unstructured grid based on a new regional DEM of ~180 m resolution and allowing refinement in many critical areas. Finally, the results have been compared to tide gauge records, field observations and testimonials from 2018. The arrival times, wave amplitude and polarities present good similarities, especially in far-field locations (Hienghène, Port-Vila and Poindimié). Maximum wave heights and energy maps for two different scenarios highlight the fact that the orientation of the source (strike of the rupture) played an important role, focusing the maximum energy path of the tsunami south of Grande-Terre and the Isle of Pines. However, both scenarios indicate similar propagation toward Aneityum, Vanuatu southernmost island, the bathymetry acting like a waveguide. This study has a significant implication in tsunami hazard mitigation in New Caledonia as it helps to validate the modelling code and process used to prepare a scenarios database for warning and coastal evacuation.

Jean Roger et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-58', Anonymous Referee #1, 21 May 2021
    • AC1: 'Reply on RC1', Jean Roger, 03 Jun 2021
  • RC2: 'Comment on nhess-2021-58', Alberto Armigliato, 23 May 2021
    • AC2: 'Reply on RC2', Jean Roger, 03 Jun 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-58', Anonymous Referee #1, 21 May 2021
    • AC1: 'Reply on RC1', Jean Roger, 03 Jun 2021
  • RC2: 'Comment on nhess-2021-58', Alberto Armigliato, 23 May 2021
    • AC2: 'Reply on RC2', Jean Roger, 03 Jun 2021

Jean Roger et al.

Jean Roger et al.

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Short summary
This study deals with the December 5, 2018 tsunami in New Caledonia and Vanuatu (southwestern Pacific) triggered by a magnitude Mw 7.5 earthquake having occurred southeast of Maré, Loyalty Archipelago and widely felt in the region. Numerical modelling results of the tsunami using a uniform slip model on a rectangular fault plane compared to real tide gauge records and testimonies are globally well correlated, especially in far-field locations.
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