M 7.0 - 234 km W of Abepura, Indonesia

Tectonic Summary

The July 27, 2015, M 7.0 earthquake near Abepura, Indonesia, occurred as the result of reverse faulting on a fault plane dipping moderately either to the northeast or southwest. The earthquake occurred in a broad zone of convergence between the Pacific and Australia plates, whose boundary in this region is divided by some authors into a series of microplates that together take up the relative motions between the larger plates. The epicenter of the July 27th event lies close to the boundaries among the Maoke, Woodlark, and Caroline microplates. At this location, the Pacific plate moves towards the southwest with respect to the Australia plate, at a rate of approximately 111 mm/yr. To the north of the event, the Pacific (Caroline) plate subducts to the southwest beneath Australia (Maoke and Woodlark) at the New Guinea Trench, and the location and mechanism of the July 27, 2015, earthquake are consistent with its occurrence on or near that slab interface at depth. Finite-fault modeling of globally recorded seismic data is more consistent with slip on a fault dipping moderately to the southwest, within the subducted lithosphere of the Caroline plate (just below the plate boundary).

The Australia:Pacific plate boundary through Papua New Guinea experiences frequent moderate to large earthquakes, and has hosted 29 other events of M 6.5+ over the prior century. The largest was a M 7.7 earthquake 150 km to the east-southeast of the July 27th event in January 1971. All of these earthquakes reflect the complex tectonics of the region, exhibiting reverse faulting mechanisms associated with Pacific subduction, as well as transform, reverse, and normal faulting mechanisms associated with upper plate deformation. None are known to have caused significant damage, likely because of the sparse population of the region.

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)