Tectonic Summary

The M 7.5, April 19, 2014, earthquake southwest of Panguna, Papua New Guinea, occurred as the result of shallow thrust faulting on or near the subduction zone interface between the Australia plate and overriding Pacific plate. At the location of the earthquake, the Australia plate moves towards the east-northeast at a velocity of about 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 consider the edge of the Australia plate to be divided into several microplates that take up the overall convergence between the Australia and Pacific plates. Here the Solomon Sea microplate moves slightly faster and more northeasterly relative to the Pacific plate than does the Australia plate due to sea-floor spreading in the Woodlark Basin several hundred kilometers to the south of the April 19th earthquake.

This event is the latest in an ongoing sequence of seismicity in the same region over the previous week, which began with M 7.1 and M 6.5 earthquakes on April 11, just to the northeast and southeast of the April 19th earthquake, respectively. Over the intervening 8 days, 45 earthquakes of M 4.5+ occurred nearby, including a M 6.6 event about 12 hours before the April 19th earthquake.

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 April 19, 2014, earthquake are typically about 80x40 km (length x width); modeling of this earthquake implies dimensions of about 50x50 km, predominantly surrounding and northwest of the hypocenter.

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 a M 8.0 event 175 km to the northwest of the April 19, 2014, earthquake, one of two M 8+ 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.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)

Event Details

Event Map

Tectonic Summary

Tectonic Summary

Historical Magnitude 4.5+ (100km)