Seismic Swarm PS20150330.1: Analysis of Activity Near Kokopo, Papua New Guinea

The seismic swarm designated PS20150330.1 occurred in a tectonically active zone 126 km south-southeast of Kokopo, Papua New Guinea. This region lies within the Pacific Ring of Fire, where complex interactions between the Pacific Plate, Australian Plate, and smaller plates such as the South Bismarck and Solomon Sea plates drive frequent seismicity. Subduction along the New Britain Trench and associated fault systems produces both shallow and intermediate-depth earthquakes, contributing to the area's elevated seismic hazard.

The swarm commenced at 23:48 on 29 March 2015 and concluded at 08:31 on 30 March 2015, spanning 8 hours and 43 minutes. During this interval, six earthquakes were recorded. The sequence opened with a magnitude 7.5 event at 41 km depth. Subsequent shocks included a magnitude 5.7 at 42 km depth, a magnitude 5.1 at 35 km depth, a magnitude 5.3 at 10 km depth, a magnitude 4.7 at 38 km depth, and a final magnitude 5.3 at 35 km depth. Depths ranged from shallow crustal levels to intermediate values, consistent with regional subduction-related seismicity.

Papua New Guinea has documented multiple earthquake swarms since 2000, with 13 recorded events. These occurred in 2000 (seven swarms), 2002 (one), 2003 (one), 2005 (one), 2011 (one), 2013 (one), and 2014 (one). Such swarms often cluster near volcanic and tectonic boundaries around the Bismarck Sea, reflecting stress adjustments along plate margins.

Notable strong earthquakes since 2000 further illustrate the region's activity. A magnitude 7.5 event struck 53 km southeast of Kokopo on 29 March 2015, 31 km from the swarm center. Another magnitude 7.5 occurred 131 km south-southwest of Kokopo on 5 May 2015, 96 km from the swarm center. Earlier, a magnitude 7.8 earthquake took place 135 km southeast of Kokopo on 16 November 2000, 59 km from the swarm center. These events highlight recurring large-magnitude seismicity along the same structural trends.

The 2015 swarm aligns with patterns of clustered aftershock-like activity following major regional ruptures, though its precise classification derives from internal monitoring criteria. Ongoing tectonic convergence in the area suggests continued potential for both isolated large events and swarm sequences.

References

SeismoSight internal classification data for swarm PS20150330.1 and historical statistics.
USGS Earthquake Catalog for regional tectonic context and strong-event parameters.
Global seismicity reviews on Papua New Guinea plate boundaries (updated through 2023 literature).