Poster of the Banda Sea Earthquake of 02 March 2005 - Magnitude 7.1

Tectonic Summary

The tectonics of the earthquake region are determined by the northward motion of the Australia plate relative to the Sunda plate at about 70 mm/yr. The relative motion of Australia toward the interior of the Sunda plate drives the motion of small plates that are situated between the Australia plate and the interior of the Sunda plate. The earthquake occurred in the inclined seismic zone that dips northward from the Timor trough and that marks the position of the subducted Australia plate. Until recently in geologic time, the Australia plate subducted beneath the Timor plate at the Timor trough. Within geologically recent time, northward subduction of Australia beneath the Timor plate has largely ceased, and the northward motion of the Australia plate relative to the Sunda plate is now accommodated substantially by the southward subduction of the Banda Sea plate beneath the Timor plate on the northern boundary of the Timor plate. The subducted Australia plate nonetheless remains intensely seismic, probably because of high stresses that are generated by the distortion of the plate.

Earthquakes, such as this one, that have focal-depths between 70 and 300 km are commonly termed intermediate-depth earthquakes. 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.