Poster of the Loyalty Islands Earthquake of 13 January 2011 - Magnitude 7.0

Tectonic Summary

The Loyalty Islands (New Hebrides trench) earthquake of January 13, 2011, occurred as the result of normal-faulting within the Australia plate, in the region of the boundary between the Australia plate and the Pacific plate. In the epicentral region of the earthquake, the Australia plate moves east-northeast relative to the Pacific plate with a velocity of about 8 cm/yr. The Australia plate subducts beneath the Pacific plate at the New Hebrides trench and is seismically active northeast of the epicenter of the January 13 earthquake to a depth of 300 km. The stresses that generated the earthquake result from the bending of the Australia plate as it subducts beneath the Pacific plate.

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 near the epicenter of the January 13 earthquake has produced 19 earthquakes of magnitude 7 or greater, the largest having magnitude 7.7.

The western margin of the Pacific plate that lies to the east of the New Hebrides trench is commonly viewed as being subdivided into several microplates that move with respect to each other at rates of a few cm/yr.

Earthquake Report

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