M7.3 - LOYALTY ISLANDS

Tectonic Summary

The Loyalty Islands (New Hebrides arc) earthquake of April 9, 2008, occurred as the result of thrust-faulting on the boundary between the Australia plate and the New Hebrides plate. In the epicentral region of the earthquakes, the Australia plate moves east-northeast relative to the New Hebrides plate with a velocity of about 11 cm/yr. The Australia plate subducts beneath the New Hebrides plate and is seismically active to a depth of about 300 km northeast of the epicenter of the April 9 earthquake.

The New Hebrides arc region of the Australia/New Hebrides plate-boundary experiences numerous strong earthquakes. In the past quarter century, the thousand kilometer section of the arc centered on the epicenter of the April 9 earthquake has produced over 20 earthquakes of magnitude 7 or greater, the largest having magnitude 7.7.