M 7.1 - 94 km SE of Gizo, Solomon Islands

Tectonic Summary

The January 3, 2010, M 7.1 Solomon Islands earthquake occurred as the result of shallow thrust faulting at the boundary where the Australia plate subducts beneath the Pacific. Focal mechanism solutions indicate that rupture occurred on either a steeply dipping reverse fault or a shallowly dipping thrust fault. At the location of the earthquake, the Australia plate moves to the northeast relative to the Pacific plate at a velocity of about 95 mm/yr, subducting at the Solomon Trench. Relative motions of the many local, small microplates help to accommodate this broad Pacific-Australia convergence and its associated back-arc spreading. In this context, the January 3rd earthquake is near the Woodlark and Solomon Sea microplates. The location, depth, and mechanism of the January 3rd earthquake are consistent with its occurrence being part of this overall subduction process.

The Solomon Islands Arc as a whole experiences a very high level of earthquake activity, and many events of M 7 or larger have been recorded since the early decades of the 20th century. The January 3rd earthquake nucleated approximately 50 km to the southeast of a M 8.1 earthquake that occurred in April 2007, which with an associated tsunami caused at least 50 fatalities and destroyed several coastal villages on nearby islands. A M 6.5 foreshock occurred less than 1 hour before the January 3, 2010, M 7.1 event, in approximately the same location.

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)