July 18, 2010 Earthquake: New Britain, Papua New Guinea

Reference #13456:

Felt (VII) at Kimbe. Also felt strongly at Kandrian and Rabaul. Felt (III) at Goroka, New Britain. Also felt at Kainantu, Port Moresby and Wau.

Tectonic Summary

The July 18, 2010, M 7.3 earthquake of New Britain, Papua New Guinea, occurred as the result of shallow thrust faulting on or near the plate boundary between the Solomon Sea and South Bismarck plates, which are 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 microplate moves approximately northward relative to the South Bismarck plate at a velocity of roughly 120 mm/yr, thrusting under the South Bismark plate at the New Britain Trench and dipping to the north-northwest. The location, depth, and focal mechanism solutions of the July 18, 2010, event are consistent with the earthquake resulting from thrust faulting associated with subduction along this plate boundary.

This earthquake occurred approximately 10 km to the north and 30 minutes after a M 6.9 earthquake. That smaller foreshock was deeper and occurred as a result of reverse faulting in a direction highly oblique to the plate convergence direction. It is thus likely that the earlier M 6.9 event occurred within the subducting Solomon Sea microplate, rather than on its thrust interface. The subducting Solomon Sea microplate is seismically active to depths of about 600 km beneath the island of New Britain.

In general, the New Britain region experiences a high level of earthquake activity, with 15 events of M 7 or larger within 3 degrees (336 km) of the July 18th event since 1973. The region also has a history of large earthquakes occurring close together in time; of those 15 events, 11 occurred within several days to months of another nearby large earthquake. In November 2000, three earthquakes of M 7.8+ occurred over a 2-day period approximately 300 km to the northeast of the July 18th earthquake. The first event (M 8.0) resulted in at least two fatalities, left many people homeless, and caused widespread damage. The second two events resulted in additional minor damage.