M 7.5; 131 km SSW of Kokopo, Papua New Guinea; (5 May 2015) (17km from the swarm center)
M 7.8; 138 km SSW of Kokopo, Papua New Guinea; (17 Nov 2000) (13km from the swarm center)
Seismic Swarm PS20030704.1: Analysis of Events Near Kokopo, Papua New Guinea
A seismic swarm designated PS20030704.1 occurred southwest of Kokopo in Papua New Guinea, beginning at 13:06 on 3 July 2003 and concluding at 03:39 on 4 July 2003. The sequence lasted 14 hours and 32 minutes, during which five earthquakes were recorded at a location 106 km southwest of Kokopo. All events originated at a focal depth of 10 km.
The swarm initiated with a magnitude 5.7 earthquake at 13:06:14 on 3 July 2003. This was followed by a magnitude 5.4 event at 15:27:26 the same day. Activity continued into 4 July with a magnitude 6.1 earthquake at 00:33:50, a magnitude 4.7 shock at 03:00:40, and a final magnitude 5.4 event at 03:39:02. The largest event reached magnitude 6.1, while the remaining shocks ranged between 4.7 and 5.7.
Papua New Guinea lies within one of the world's most tectonically active zones, situated at the complex boundary between the Pacific, Australian, and several smaller plates. The region experiences frequent seismicity driven by subduction along the New Britain Trench and associated transform faults. Historical records indicate persistent earthquake activity, with multiple swarms documented since 2000. In total, seven swarms have been identified in the area since 1 January 2000, including six events in 2000 and one in 2002.
Notable strong earthquakes have also occurred nearby since 2000. A magnitude 7.8 event struck 138 km southwest of Kokopo on 17 November 2000, only 13 km from the 2003 swarm center. A magnitude 7.5 earthquake occurred 131 km south-southwest of Kokopo on 5 May 2015, 17 km from the swarm center. Most recently, a magnitude 7.0 shock was recorded 119 km east of Kimbe on 10 October 2018, 69 km from the swarm center.
Such swarms and large events underscore the ongoing crustal deformation in the Bismarck Sea region. The shallow depths of the 2003 swarm events align with typical patterns of upper-crustal faulting in this convergent margin setting. Monitoring of these sequences contributes to improved understanding of seismic hazard in Papua New Guinea.
References
USGS Earthquake Catalog (historical events)
SeismoSight internal swarm classification (PS20030704.1 data)