Seismic Swarm PS20001116.2: Analysis of the November 2000 Events Near Kokopo, Papua New Guinea

On November 16, 2000, a seismic swarm designated PS20001116.2 was recorded 163 km east-southeast of Kokopo, Papua New Guinea. The sequence began at 05:11 and concluded at 11:05, spanning 5 hours and 54 minutes during which 28 earthquakes were registered. The events clustered at shallow depths, predominantly around 33 km, with one notable exception at 30 km. Magnitudes ranged from 4.8 to a peak of 7.8, highlighting a rapid escalation followed by sustained aftershock activity.

The swarm initiated with moderate events, including a 5.8 magnitude quake at 05:11:18 and a 6.0 at 05:21:22. Subsequent shocks maintained magnitudes above 5.0 for several hours, building toward the mainshock of 7.8 at 07:42:16. This event was followed closely by a 6.5 magnitude quake at 07:45:32. Activity continued with numerous events between 5.0 and 5.7 through the morning, culminating in a 6.2 magnitude shock at 11:05:41. Depths remained consistent, indicating a localized source within the upper crust.

Papua New Guinea lies within the tectonically complex boundary between the Pacific and Australian plates. The region around Kokopo, in East New Britain, experiences intense deformation along the New Britain Trench, where the Solomon Sea Plate subducts beneath the Bismarck Plate. This subduction drives frequent seismicity and volcanism, including activity at nearby volcanoes such as Rabaul Caldera. Shallow crustal faults and the broader plate interface accommodate convergence rates exceeding 10 cm per year, producing both megathrust and intraslab earthquakes.

Historical records since 2000 show this swarm as the sole event of its classification in the area. Strong earthquakes nearby include a magnitude 7.8 event on the same day, centered 135 km southeast of Kokopo and 14 km from the swarm centroid. Additional significant shocks comprise a 7.9 magnitude quake in 2016 located 140 km east, a 7.5 magnitude event in 2015 at 53 km southeast, and a 7.6 magnitude shock in 2005 positioned 135 km east. These occurrences underscore the persistent seismic hazard in the region.

The 2000 swarm illustrates typical behavior in subduction zones, where foreshock sequences can precede or accompany larger ruptures along the plate interface. Shallow depths facilitated efficient energy release, contributing to the observed magnitude progression. Ongoing monitoring by regional networks continues to track such activity, aiding in hazard assessment for populated centers like Kokopo.

References USGS Earthquake Catalog Global CMT Project SeismoSight internal swarm classification database