Seismic Swarm PS20141012.1 Near Kokopo, Papua New Guinea

On 12 October 2014, a seismic swarm designated PS20141012.1 occurred 138 km south of Kokopo, Papua New Guinea. The sequence began at 19:03 local time and concluded at 23:39, spanning 4 hours and 35 minutes during which seven earthquakes were recorded. Event magnitudes ranged from 4.2 to 5.3, with most occurring at depths of 35 km. The individual events unfolded as follows: a magnitude 5.2 quake at 19:03:54 (16 km depth), followed by magnitude 4.2 at 19:11:32 (36 km), magnitude 5.1 at 19:34:23 (35 km), magnitude 5.3 at 19:41:52 (35 km), magnitude 5.2 at 19:54:46 (35 km), magnitude 5.1 at 20:57:59 (35 km), and magnitude 5.0 at 23:39:20 (35 km).

This swarm reflects the intense tectonic activity characteristic of the Papua New Guinea region, situated along the Pacific Ring of Fire at the convergent margin where the Solomon Sea Plate subducts beneath the South Bismarck Plate. The resulting New Britain Trench and associated volcanic arc drive frequent seismicity, with intermediate-depth events often linked to slab dehydration and stress accumulation within the subducting lithosphere. Historical records since 2000 indicate 17 prior swarms in the vicinity, occurring in 2000 (7 events), 2002 (1), 2003 (1), 2005 (2), 2006 (3), 2010 (1), 2011 (1), and 2013 (1). These episodic clusters underscore the area's propensity for short-duration earthquake sequences amid ongoing plate convergence at rates exceeding 10 cm per year.

Notable larger events have also punctuated the region's seismic history. Since 2000, three magnitude 7.5 or greater earthquakes struck nearby: a magnitude 7.8 event on 17 November 2000 located 138 km SSW of Kokopo (45 km from the 2014 swarm center), a magnitude 7.5 on 29 March 2015 situated 53 km SE of Kokopo (86 km from the swarm center), and another magnitude 7.5 on 5 May 2015 positioned 131 km SSW of Kokopo (34 km from the swarm center). Such megathrust and intraslab ruptures highlight the potential for significant energy release along this plate boundary.

The 2014 swarm, confined to a narrow temporal window and moderate magnitudes, likely represents stress adjustment within the subducting slab rather than a foreshock sequence to a larger rupture. Depths predominantly near 35 km align with the typical range for intermediate-depth seismicity in this subduction zone, where phase transitions in the slab can trigger brittle failure. Continued monitoring remains essential given the region's elevated seismic hazard and proximity to populated centers on New Britain.

References

USGS Earthquake Catalog (historical events and regional tectonics)
SeismoSight internal swarm classification PS20141012.1