Deadly Mw7.3 earthquake shakes Vanuatu
An intra-plate event along a noisy subduction zone

This earthquake occurred along a fast-moving subduction zone, where oceanic crust of the northeastern Australia Plate is subducting beneath oceanic crust of another small tectonic plate at a rate of about 10 centimeters per year. The overriding plate is known to geologists as the New Hebrides Plate, and it is on that plate that the volcanic islands of Vanuatu have developed.

cit from: Judith and Kyle from Earthquake Insights