The region between New Caledonia and Vanuatu is located in the Southwest Pacific on the Australian Plate. It is part of the Ring of Fire “one of the most intense seismic active zones of the world” (LeMonde, 2017). Earthquakes in New Caledonia are caused, for most, by the tectonic of the Vanuatu Island Arc because of the phenomenon of subduction of the Australian plate below the Pacific plate. Earthquakes can reach a maximum magnitude of 8.0. A local seismicity exists in the south of New Caledonia is due to the reactivation of ancient fault lines.
A first one tremor was felt at 8.27 pm local time on 18th of November. A first earthquake had occurred with an intensity of 6.4 on the Richter scale (according to USGS). Then, a second one occured at 2.10 am local time in the night of 18th and 19th November with an intensity of 6.6 on the Richter scale. The epicentre was located in the East of the Mare Island around twenty kilometres deep (according to USGS).
On 20th of November, it’s a 7 magnitude earthquake which was felt at 9.44 am local time about 85 kilometres from the East of Loyalty Islands which is close to 25 kilometres of depth (according to USGS). The latter one caused the trigger of the Tsunami warning following observations of “disorders move of the sea level” (radio Canada, 2017). This warning was lifted after 1 hour. The coastal population from nearby islands was evacuated. According to local authorities, there is no serious damage. However, authorities said “people can go back to work but they have to stay careful. There are many repeats.” (francetvinfo.fr)
These earthquakes were not the last ones. The 31 of October, a 6.8 magnitude earthquake was felt in Mare Island. Next 8 days were marked by about 300 tremors with different intensities everywhere in the archipelago. Earthquakes are common in this part of the world.
[Article rédigé 21/11/17]
Sources :
« Un séisme de magnitude 7 à l’est de la Nouvelle-Calédonie ne fait pas de dégât notable », 20/11/17, Le Monde URL : http://www.lemonde.fr/planete/article/2017/11/20/un-seisme-de-magnitude-7-a-l-est-de-la-nouvelle-caledonie-risque-de-vagues-de-tsunami_5217335_3244.html
« Nouvelle-Calédonie : un puissant séisme de magnitude 7 ne fait pas de dégâts notables », 20/11/17, Francetvinfo
« Séisme de magnitude 6,5 en Nouvelle-Calédonie, pas de risque de tsunami », 30/10/17, Tahiti-infos.com
Site dédié aux séismes en Nouvelle-Calédonie : http://www.seisme.nc/index.php?option=com_content&view=article&id=55&Itemid=197&lang=fr