The earthquake occurred in a tectonically complex region where the Australian Plate moves towards the east-northeast relative to the Pacific Plate. It moves at a velocity of about 100 mm (4 in)/yr. Earthquakes in this geographical region are generally associated with the large-scale convergence of these two major plates and with the complex interactions of several associated microplates, most notably the South Bismarck Plate, the Solomon Sea microplate, and the Woodlark Plate.[1]