M 7.5; 131 km SSW of Kokopo, Papua New Guinea; (5 May 2015) (48km from the swarm center)
M 7.0; 72 km ESE of Kimbe, Papua New Guinea; (4 Aug 2010) (82km from the swarm center)
M 7.8; 138 km SSW of Kokopo, Papua New Guinea; (17 Nov 2000) (38km from the swarm center)
Seismic Swarm PS20181010.1: Insights into Earthquake Activity Near Kokopo, Papua New Guinea
On 10 October 2018, a seismic swarm designated PS20181010.1 was recorded 91 km southwest of Kokopo, Papua New Guinea. The sequence began at 20:45 local time and concluded at 22:00, encompassing five earthquakes within a span of 1 hour and 15 minutes. The events registered magnitudes of 6.1, 7.0, 5.9, 5.9, and 6.2, with focal depths ranging from 19 km to 121 km.
This swarm occurred within the tectonically active Bismarck Archipelago, part of Papua New Guinea’s position along the Pacific Ring of Fire. The region experiences intense seismicity due to the convergence of the Pacific Plate and the Australian Plate, involving subduction along the New Britain Trench and associated strike-slip faulting. These interactions produce frequent moderate to large earthquakes, often at shallow to intermediate depths.
Historical records since 2000 indicate 23 prior swarms in the area, with notable clusters in 2000 (four events), 2015 (five events), and single or paired occurrences in intervening years. Strong earthquakes nearby include a magnitude 7.0 event 119 km east of Kimbe on the same day as the swarm, a magnitude 7.5 quake 131 km south-southwest of Kokopo in 2015, a magnitude 7.0 event 72 km east-southeast of Kimbe in 2010, and a magnitude 7.8 shock 138 km south-southwest of Kokopo in 2000. These highlight recurring high-magnitude potential within tens of kilometers of the swarm center.
Swarm sequences like PS20181010.1 typically reflect fluid migration or stress redistribution along fault networks rather than a single mainshock-aftershock pattern. Depths between 19 km and 121 km align with the complex crustal and subducting slab structure in this arc setting, where intermediate-depth events can signal slab dehydration processes.
Such activity underscores the ongoing seismic hazard in Papua New Guinea, where population centers like Kokopo remain exposed to both swarm-related shaking and larger isolated ruptures.
References
USGS Earthquake Catalog (earthquake.usgs.gov)
Global CMT Catalog (globalcmt.org)
SeismoSight internal swarm classification data