Seismic Swarm PS20150509.1: Context and Analysis in Papua New Guinea

The seismic swarm designated PS20150509.1 occurred on 9 May 2015, approximately 181 km east-southeast of Kimbe, Papua New Guinea. The sequence began at 03:27 and concluded at 11:14 local time, spanning 7 hours and 46 minutes. During this interval, five earthquakes were recorded, with magnitudes ranging from 4.3 to 5.5 and focal depths between 10 km and 60 km. The events included a 5.2 magnitude quake at 03:27:27 (23 km depth), followed by a 5.4 at 09:42:35 (12 km), a 5.5 at 09:42:42 (60 km), a 4.3 at 11:11:08 (10 km), and a final 5.4 at 11:14:24 (20 km). Such clustered activity reflects the dynamic stress release typical of subduction-related settings.

Papua New Guinea occupies a tectonically complex zone at the convergence of the Pacific, Australian, and Philippine Sea plates. The New Britain region, where the swarm was centered, lies along the New Britain Trench, an active subduction boundary that drives frequent seismicity and volcanism. This arc system produces intermediate-depth earthquakes as the downgoing slab interacts with the overriding plate. Historical data indicate persistent swarm activity since 2000, with 20 documented swarms occurring in 2000 (6), 2003 (1), 2005 (2), 2006 (3), 2010 (2), 2011 (1), 2013 (1), 2014 (1), and 2015 (3). These episodes highlight episodic strain accumulation and release within the subduction interface.

Notable large-magnitude earthquakes have also struck nearby. A magnitude 7.8 event on 17 November 2000 was located 33 km from the swarm center, while a magnitude 7.5 quake on 5 May 2015 occurred 37 km away. More recently, a magnitude 7.0 earthquake on 10 October 2018 was situated 67 km distant. These events underscore the region’s capacity for both swarm-type sequences and isolated great earthquakes, consistent with the mechanics of oblique subduction and slab dehydration processes.

The 2015 swarm’s shallow-to-intermediate depths align with typical patterns observed along the Bismarck Sea segment of the plate boundary. Ongoing monitoring by regional networks continues to track such activity, contributing to improved understanding of seismic hazards in this high-risk arc environment.