M 7.0 - 119 km E of Kimbe, Papua New Guinea

Tectonic Summary

The October 10, 2018, M 7.0 earthquake east of Kimbe, Papua New Guinea, occurred as the result of thrust faulting on or near the plate boundary interface between the subducting Australia and overriding Pacific plates. At the location of the earthquake, the Australia plate moves towards the east-northeast at a velocity of 105 mm/yr with respect to the Pacific plate, and begins its subduction into the mantle beneath New Britain at the New Britain Trench, south-southeast of the earthquake. The moment tensor and depth of the event are consistent with thrust-type motion on the interface between these two plates. Note that at the location of the earthquake, some researchers consider the edges of the Australia and Pacific plates to be divided into several microplates that take up the overall convergence between the Australia and Pacific plates, including the Solomon Sea and South Bismark microplates local to this event. The Solomon Sea microplate moves slightly faster and more northeasterly with respect to the Pacific plate than does the Australia plate due to sea-floor spreading in the Woodlark Basin several hundred kilometers to the southeast of the October 10th earthquake, facilitating the classic subduction evident beneath New Britain.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Thrust-faulting events of the size of the October 10, 2018, earthquake are typically about 40x20 km (length x width).

The plate boundary between the Australia and Pacific plates in the Papua New Guinea region is very active seismically; 28 M 7+ events have occurred within 250 km of the October 10, 2018 earthquake over the preceding century. Few are known to have caused shaking-related fatalities because of the remoteness of the region, though a M 8.0 earthquake in November 2000—one of three similarly sized events over a 2-day period—did cause several deaths. A M 7.2 earthquake in May 1985, just 20 km to the northwest of the October 10, 2018 earthquake, also resulted in one fatality, though that event was a strike-slip earthquake in the upper plate, much shallower than today’s shock. The largest nearby earthquake was a M 8.1 event, 250 km to the northeast of the October 10, 2018, earthquake.

The October 10th earthquake was preceded by several minutes by a M 5.9 earthquake, just to the southeast of the M 7.0 event. In the two hours since the M 7.0 earthquake, several aftershocks have also occurred, including two moderate-sized (M 5.7 and M 5.9) events just to the southwest, and a larger M 6.2 shock 100 km to the northeast and at a depth of about 120 km, within the subducting Australia slab rather than on the interface between the two plates.