M 7.1 - 118 km S of Isangel, Vanuatu

Tecotonic Summary

The December 7, 2023, M 7.1 Vanuatu earthquake occurred as the result of reverse faulting east of the South New Hebrides Trench in the southeast Pacific Ocean. The location and depth of the earthquake indicate that it occurred on or near an eastward-dipping subduction zone that defines the interface between the Australia plate and the New Hebrides microplate (a component of the larger Pacific plate). At the location of the earthquake, the Australia plate subducts to the east-northeast beneath the islands of Vanuatu and the New Hebrides microplate at a rate of about 79 mm/yr. The December 7 earthquake’s location, depth, and focal mechanism solutions are consistent with the earthquake resulting from northeastward-dipping thrust faulting associated with subduction along this plate boundary.

The Vanuatu region experiences a very high level of earthquake activity, with 27 earthquakes of M 7 or larger occurring within 250 km of the December 7, 2023 earthquake in the past century. In February 1990 and March 2007, M 7.0 and M 7.1 earthquakes exhibited nearly identical locations to this 2023 earthquake. Because these previous earthquakes were remote, large population centers were not exposed to strong shaking. Therefore, no significant damage was reported from the 1990 and 2007 events.