Seismic Swarm PS20111107.1 Near Kavieng, Papua New Guinea

On 7 November 2011, a seismic swarm designated PS20111107.1 was recorded 147 km southwest of Kavieng, Papua New Guinea. The sequence began at 00:43 UTC and concluded at 11:37 UTC, spanning 10 hours and 53 minutes. Five earthquakes were detected during this interval, with magnitudes ranging from 4.4 to 5.3 and focal depths between 10 km and 46 km.

The events occurred in close temporal succession. The initial shock registered magnitude 5.0 at 46 km depth, followed by a magnitude 5.3 event at 23 km depth roughly one hour later. Subsequent shocks included magnitudes 5.1 at 35 km and 5.3 at 41 km, before the sequence ended with a magnitude 4.4 event at 10 km depth. Depths clustered primarily in the upper crust and uppermost mantle, consistent with regional tectonic deformation.

Papua New Guinea lies within the Pacific Ring of Fire, where complex interactions among the Pacific, Australian, and several microplates drive intense seismicity. The swarm location falls in the Bismarck Sea region, influenced by oblique convergence along the New Britain subduction zone and associated transform boundaries. This setting produces frequent moderate earthquakes, often in clusters, as stresses accumulate and release along fault systems accommodating plate motion rates exceeding 10 cm per year in places.

Historical records maintained by SeismoSight indicate only two swarms have occurred in the area since 1 January 2000. The preceding swarm took place in 2002 and consisted of a single event cluster. The 2011 sequence therefore represents the second documented swarm in more than a decade, underscoring the episodic nature of seismic activity in this segment of the plate boundary.

Such swarms provide insight into transient stress changes within the crust. The rapid succession of events, without a dominant mainshock-aftershock pattern, suggests fluid migration or aseismic slip may have contributed to triggering. Depths transitioning from deeper to shallower levels during the sequence align with typical patterns observed in subduction-related forearc environments.

Continued monitoring by regional networks remains essential for understanding long-term seismic hazards in Papua New Guinea, where population centers lie near active tectonic features.

References
USGS Earthquake Catalog (historical regional seismicity)
Global CMT Project (tectonic framework)
SeismoSight internal swarm classification records