M7.3 - VANUATU

Tectonic Summary

The Vanuatu earthquake of August 10, 2010 occurred on or near the plate boundary between the Australia and Pacific plates in the Coral Sea region of the southwest Pacific. In the region of the earthquake, the Australia plate moves to the east-northeast with respect to the Pacific plate at a velocity of approximately 85 mm/year. The Australia plate thrusts underneath the Pacific plate at the Vanuatu trench and dips to the east-northeast. The August 10 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.

This earthquake is located approximately 500 km to the south of a sequence of large subduction thrust earthquakes that occurred in October of 2009. On October 7th, 2009, two earthquakes of M 7.7 and M 7.8 occurred 15 minutes apart. After these events, an M 7.4 aftershock struck approximately one hour later, and two M 6.6 and M 6.8 aftershocks occurred on the following day. On May 27th, 2010, a M 7.1 earthquake occurred a further 100 km to the north of the October 2009 sequence.

The Vanuatu region experiences a very high level of earthquake activity, with almost 50 events of magnitude 7 and larger having been recorded since 1973. The subducting Australia plate is seismically active to depths of about 350 km beneath the islands.