M7.2 - SANTA CRUZ ISLANDS

Tectonic Summary

The Santa Cruz Islands earthquake of September 2, 2007, occurred along the boundary between the Pacific plate and Australia 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/y. The Australia plate thrusts under the Pacific plate at the North New Hebrides trench and dips to the east-northeast. The September 2 earthquake’s location and focal mechanism are consistent with the earthquake having occurred as thrust-faulting on the plate interface.

The Santa Cruz Islands region experiences a very high level of earthquake activity, with over a dozen shocks 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 250 km beneath the islands