A Mw 7.0 earthquake occurred east of New Caledonia and the Loyalty Islands (21.325°S, 168.672°E) on 2017-11-19 22:43 UTC, generating a small tsunami. The earthquake occurred as the result of shallow normal faulting within the oceanic crust of the Australia plate, just west of the South New Hebrides Trench which marks the plate boundary between the Australia and Pacific plates in this region. At the location of this earthquake, the Australia plate moves towards the east-northeast with respect to the Pacific at a rate of approximately 78 mm/yr. At the New Hebrides Trench, Australia lithosphere converges with and sinks beneath the Pacific plate, descending into the mantle and forming the New Hebrides/Vanuatu subduction zone. The earthquake occurred approximately 20 km to the west of this trench, in the tectonic region sometimes known as the "outer rise," where the subducting plate begins flexing (extending) before sinking into the mantle. The effects of the tsunami were mainly confined to nearby islands.

The 19 November earthquake was one of many M 6+ earthquakes that were part of an intense sequence of events that began on 31 October 2017. Over this time period, about 135 M 4+ earthquakes were recorded in this region by the USGS, most to the west of the plate boundary, in the outer rise.

The Loyalty Islands region is very active seismically, and the region within 250 km of the 19 November 2017 earthquake has hosted 21 other M 7+ earthquakes over the preceding century, including an M 8.1 earthquake in 1920, and a M 7.7 earthquake in 1995. Four of these occurred in the outer rise area to the east of the trench.

Top: Regional tectonics and seismicity M7 or greater by depth. Epicenter of the 19 November Mw 7.0 earthquake is shown by the yellow star. Bottom: Geographic setting.