April 19, 2014 Earthquake: Solomon Sea, Papua New Guinea

Tectonic Summary

The M 7.5 April 19, 2014 earthquake southwest of Panguna, Papua New Guinea, occurred as the result of thrust faulting on or near the subduction zone interface between the subducting Australia plate and overriding Pacific plate. At the location of the earthquake, the Australia plate moves towards the east-northeast at a velocity of 102 mm/yr with respect to the Pacific, and begins its subduction into the mantle beneath Bougainville Island at the New Britain Trench south 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 divide the edge of the Australia plate into several microplates that take up the overall convergence between Australia and the Pacific. Here the Solomon Sea plate moves slightly faster and more northeasterly with respect to the Pacific plate than does Australia due to sea-floor spreading in the Woodlark Basin several hundred kilometers to the south of the April 19 earthquake.

This event is the latest in an ongoing sequence of seismicity in the same region over the past week, which began with M 7.1 and 6.5 earthquakes on April 11, just to the northeast and southeast of the April 19 earthquake, respectively. Over the intervening eight days, 45 earthquakes of M 4.5 or greater have occurred nearby, including a M 6.6 event about 12 hours before the April 19 earthquake.

In the Papua New Guinea region, the boundary between Australia and Pacific plates is very active seismically; 35 M 7+ events have occurred within 250 km of the April 19, 2014 earthquake over the past century. None are known to have caused any shaking-related fatalities. The largest was an M 8.0 175 km to the northwest of the April 19, 2014 earthquake, one of two M8+ earthquakes 140 km apart in July 1971. The M 8.1 Solomon Islands earthquake in April 2007, which caused a devastating tsunami, was 300 km southeast of the April 19, 2014 event.

(above from reference #13456)