M 7.9; 140 km E of Kokopo, Papua New Guinea; (17 Dec 2016) (84km from the swarm center)
M 7.5; 53 km SE of Kokopo, Papua New Guinea; (29 Mar 2015) (26km from the swarm center)
M 7.6; 135 km E of Kokopo, Papua New Guinea; (9 Sep 2005) (78km from the swarm center)
M 7.8; 135 km SE of Kokopo, Papua New Guinea; (16 Nov 2000) (62km from the swarm center)
Seismic Swarm PS20001116.4: November 2000 Activity near Kokopo, Papua New Guinea
A seismic swarm designated PS20001116.4 occurred southeast of Kokopo, Papua New Guinea, from 15:23 on 16 November 2000 to 04:44 on 21 November 2000. Over 109 hours and 20 minutes, 29 earthquakes were recorded at a location 128 km SSE of Kokopo. Magnitudes ranged from 4.9 to 6.1, with the majority at depths of 33 km and one event at 63 km. The sequence began with a 5.6 magnitude shock and included multiple events above magnitude 5.0, peaking with a 6.1 magnitude earthquake on 18 November.
This swarm unfolded in a tectonically complex region where the Pacific Plate subducts beneath the Australian Plate along the New Britain Trench. The area forms part of the Bismarck Volcanic Arc, characterized by frequent intermediate-depth and shallow crustal seismicity driven by oblique convergence and back-arc spreading. Historical records confirm elevated earthquake rates, consistent with the subduction dynamics that accommodate rapid plate motion.
The swarm coincided temporally with a magnitude 7.8 earthquake on 16 November 2000 located 135 km SE of Kokopo. Subsequent strong events in the broader region include a magnitude 7.6 in 2005, a magnitude 7.5 in 2015, a magnitude 7.9 in 2016, and a magnitude 7.6 in 2019, all within 26–84 km of the swarm epicentral area. These events underscore the persistent seismic hazard along the plate boundary.
Since 2000, only one additional swarm has been documented in the immediate vicinity, highlighting the relative rarity of such clustered sequences compared with isolated mainshock-aftershock patterns. Depths predominantly near 33 km align with typical crustal faulting above the subducting slab, while the single deeper event at 63 km may reflect activity within the downgoing plate.
Analysis of the temporal distribution shows clustering of higher-magnitude events between 18 and 19 November, followed by a decline toward the swarm’s termination. Such patterns are common in subduction-related swarms, where stress transfer along the megathrust and overlying crust can sustain elevated seismicity for several days without a single dominant mainshock.
References
U.S. Geological Survey Earthquake Catalog
Global Seismographic Network bulletins
SeismoSight internal swarm classification PS20001116.4