M 7.1 - 125 km W of Port-Vila, Vanuatu

Tectonic Summary

The February 2, 2012, M 7.1 earthquake near Vanuatu in the southwest Pacific Ocean occurred as a result of shallow, oblique normal faulting within the lithosphere of the Australia plate. Focal mechanism solutions indicate that oblique rupture occurred on either a northeast- or south-southeast-striking, moderately dipping normal fault. The earthquake epicenter is located just 15 km to the west of the New Hebrides Trench, the bathymetric expression of the boundary between the Australia and Pacific plates, where lithosphere of the Australia plate subducts into the mantle beneath the North Fiji Basin. Slip on a fault aligned with either nodal plane of the focal mechanism solution is consistent with this intraplate setting. At the location of this earthquake, the Australia plate moves east-northeast with respect to the Pacific plate at a velocity of approximately 84 mm/yr.

The Vanuatu region frequently experiences earthquakes of this size; about a dozen earthquakes of M 7 or larger have occurred within 250 km of the February 2nd event over the past 30 years. However, they generally occur on the megathrust interface to the east, and few have been outboard (seaward) of the trench. A M 7.3 normal faulting earthquake did occur to the west of the New Hebrides Trench, about 225 km to the south of the February 2nd event, on December 25, 2010.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)