Seismic Swarm PS20211130.1: Analysis of Activity Southeast of Kavieng, Papua New Guinea

A seismic swarm designated PS20211130.1 occurred on 30 November 2021, approximately 121 km south-southeast of Kavieng in Papua New Guinea’s New Ireland Province. The sequence began at 10:36 local time and concluded at 12:14, spanning 1 hour and 38 minutes. During this interval, six earthquakes were recorded, all at a focal depth of 10 km. Magnitudes ranged from 5.0 to 6.3, with the largest event (6.3) occurring at 10:36:18, followed closely by a 6.1 event at 10:37:35. Subsequent shocks measured 5.0 at 10:52:17, 5.0 at 11:09:37, and 5.0 at 11:14:07, closing with a 5.8 event at 12:14:34.

This swarm reflects clustered seismicity typical of the tectonically complex Bismarck Sea region. Papua New Guinea lies within the Pacific Ring of Fire, where interactions among the Australian, Pacific, and Solomon Sea plates drive frequent earthquakes and volcanic activity. The New Ireland area experiences oblique subduction and strike-slip faulting along the Bismarck Sea seismic lineament, producing shallow crustal events that align with the observed 10 km depths.

Historical records indicate three prior swarms in the same region since 1 January 2000: one in 2002 and two in 2011. These earlier episodes demonstrate recurring, short-duration clustering rather than isolated mainshock-aftershock sequences. Swarm PS20211130.1 fits this pattern, with rapid onset of multiple moderate-magnitude events over a narrow time window and no single dominant mainshock.

Such swarms provide insight into stress transfer along local fault networks. The tight temporal spacing and consistent shallow depths suggest fluid migration or aseismic slip may have contributed to triggering successive ruptures. Monitoring these episodes aids in refining regional hazard models, particularly given Papua New Guinea’s exposure to both seismic and tsunami risks.

References

• SeismoSight internal swarm classification database
• Geological Survey of Papua New Guinea regional tectonic summaries
• Pacific Ring of Fire seismicity reports (updated through 2023)