Update of the tsunami catalogue of New Caledonia using a decision table based on seismic data and maregraphic records

Abstract

Abstract. 14 years ago, the December 26, 2004 Indian Ocean tsunami brought to the entire World the destruction capability of tsunamis. Since then, many research programs have been initiated to try to better understand the phenomenon and its related hazards, and to improve the early warning systems for the exposed coastal populations. Pacific Islands Countries and Territories (PICTs) are especially vulnerable to tsunamis. Amongst them, New Caledonia is a French overseas territory located in the South-western Pacific and exposed to several tsunamis sources. In 2010, a catalogue of tsunamis that were visually observed or measured in New Caledonia was published. Since this first study, several events occurred between 2009 and 2019 and an update of this catalogue was necessary within the framework of a tsunami hazard assessment project (TSUCAL). To complete this catalogue, a decision algorithm has been designed to select potential tsunamigenic events within the USGS earthquake database, using criteria on the distance to New Caledonia, the magnitude and the hypocenter depth. Then a cross-comparison between these earthquake events, the NOAA NGDC tsunami catalogue and local tide gauge records provided 25 events that were recorded in New Caledonia for the period from September 30, 2009 to January 10, 2019. These events are added to the 12 events reported with certainty during previous studies, leading to a number of 37 tsunamis triggered by earthquakes reported in New Caledonia since 1875. Six of them have been identified only thanks to local tide gauges, supporting the fact that instrumental recording of tsunamis is paramount for tsunami hazard studies, from early warning to the validation of coastal models. In addition, previously unpublished data is provided for other already reported tsunamis as well as tsunamis with unspecified date and source.

Earthquake Fingerprint of an Incipient Subduction of a Bathymetric High

“…This thrust event was followed by a month-long swarm of normal-faulting earthquakes (10 events with M w > 6) illuminating ∼100 × 80 km 2 area of the LR (Figure 3). Within the first 24 hr, three large normal events (M w > 6) occurred with the largest M w 6.7 triggering another small tsunami (Roger et al, 2019) (Figures 3 and 4a). The seismicity then gradually expanded northward, where on 19 November a M w 7 earthquake struck a few hours after two M w 6.3 and 6.7 events (Figures 3 and 4a).…”