M7.7 - VANUATU

Tectonic Summary

The Torres Islands, Vanuatu earthquake of October 7, 2009, occurred on or near the plate boundary between the Australia and Pacific plates. In the region of the earthquake, the Australia plate moves to the east-northeast with respect to the Pacific plate at a velocity of about 91 mm/year. The Australia plate thrusts under the Pacific plate at the New Hebrides trench and dips to the east-northeast. The October 7 earthquake’s location, depth, and focal mechanism are consistent with the earthquake having occurred as thrust-faulting associated with subduction along the Australia-Pacific plate boundary.

The Vanuatu region experiences a very high level of earthquake activity, with over a dozen events of magnitude 7 and larger having been recorded since the early decades of the twentieth century. The subducting Australia plate is seismically active to depths of about 350 km beneath the islands.

Recent large earthquakes near the October 7 event include a M 7.2 earthquake in 2007 and a M 7.3 earthquake in 1999.