Poster of the New Ireland Earthquake of 09 September 2005 - Magnitude 7.7

Tectonic Summary

This intermediate-depth earthquake occurred within the lithosphere of the Solomon Sea plate, which is subducting generally to the north beneath the North Bismarck plate and the South Bismarck plate. The Solomon Sea, North Bismarck, and South Bismarck plates are all small plates within the broad region of convergence between the Australia plate and the Pacific plate. In this region, the Australia plate moves to the east-northeast with respect to the Pacific plate with a velocity of about 100 mm/yr. Earthquakes such as this one, that have focal-depths between 70 and 300 km, are commonly termed "intermediate-depth" earthquakes. Intermediate-depth earthquakes represent deformation within subducted plates, rather than deformation at plate boundaries. Intermediate-depth earthquakes typically cause less damage on the ground surface above their foci than is the case with similar magnitude shallow-focus earthquakes, but large intermediate-depth earthquakes may be felt at great distance from their epicenters. The Solomon Sea plate in this region is seismically active to depths of over 500 km


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