M7.0 - NEW BRITAIN REGION, PAPUA NEW GUINEA

Tectonic Summary

The New Britain, Papua New Guinea earthquake of August 4, 2010 (22:01 GMT) occurred as a result of thrust faulting on or near the plate boundary between the Solomon Sea and South Bismarck plates, microplates involved in the accommodation of large-scale convergence between the Australia and Pacific plates in the Woodlark Basin region of the southwest Pacific. At the location of this earthquake, the Solomon Sea plate moves approximately northwards with respect to the South Bismarck plate at a velocity of roughly 120 mm/year, thrusting under the South Bismark plate at the New Britain trench and dipping to the north-northwest. The August 4, 2010 earthquake's location, depth, and focal mechanism are consistent with the earthquake having occurred as thrust faulting associated with subduction along this plate boundary. The subducting Solomon Sea plate is seismically active to depths of about 600 km beneath the island.

The New Britain region experiences a high level of earthquake activity, with 16 events of magnitude 7 and larger having been recorded within 3 degrees (336 km) of this event since 1973. The region also has a history of large earthquakes occurring close together in time; of those 16 events, 12 occurred within several days-to-months of another nearby large earthquake. On July 18, 2010 two earthquakes (M6.9 and a M7.3) struck about 25 km to the southwest of the August 4, 2010 earthquake. In November 2000, three earthquakes of M7.8 or larger occurred over a two day period approximately 275 km to the northeast of the August 4, 2010 earthquake.

Earthquake Information for Papua New Guinea