At the location of this earthquake, the Australia plate moves towards the east-northeast with respect to the Pacific at a rate of approximately 75 mm/yr. At the South 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, stretching from New Caledonia in the south to the Santa Cruz Islands in the north, a distance of about 1,600 km.
https://earthquake.usgs.gov/earthquakes/eventpage/us6000dg77/executive