Seismic Swarm PS20161224.1 Southeast of Kokopo, Papua New Guinea

The seismic swarm PS20161224.1 was recorded southeast of Kokopo in Papua New Guinea, beginning at 21:28 on 23 December 2016 and concluding at 23:34 on 24 December 2016. Over this 26-hour period, seven earthquakes occurred at a location 201 km southeast of Kokopo. Magnitudes ranged from 4.5 to 6.0, with focal depths between 10 km and 47 km. The sequence included events at 5.0 (10 km), 5.0 (47 km), 6.0 (35 km), 5.8 (30 km), 4.5 (10 km), 5.0 (14 km), and 5.0 (10 km).

Papua New Guinea lies within the Pacific Ring of Fire, where complex interactions among the Pacific, Australian, and several microplates drive intense seismic activity. The swarm region southeast of Kokopo sits near the New Britain subduction zone, where the Solomon Sea Plate descends beneath the South Bismarck Plate. This tectonic setting produces frequent moderate to large earthquakes along the arc and associated transform boundaries.

The swarm reflects typical clustered seismicity in a subduction environment. Most events occurred at shallow to intermediate depths, consistent with activity along the plate interface or within the overriding crust. No single mainshock dominated the sequence, distinguishing it from typical aftershock patterns.

Since 1 January 2000, twenty-two swarms have been documented in the broader region. These occurred in 2000 (seven swarms), 2007 (one), 2013 (one), 2014 (six), 2015 (four), and 2016 (three). Such recurrent swarms indicate persistent stress accumulation and release along the subduction interface.

A notable prior event was the magnitude 7.8 earthquake on 16 November 2000, located 135 km southeast of Kokopo and approximately 87 km from the 2016 swarm center. This quake underscores the potential for larger ruptures in the same tectonic corridor.

Ongoing monitoring of swarm activity helps refine understanding of subduction-zone behavior and supports regional hazard assessment in this highly active margin.