Seismic Swarm PS20110616.1 Near Kimbe, Papua New Guinea: Geological Context and Event Analysis

The seismic swarm designated PS20110616.1 occurred approximately 143 km east-southeast of Kimbe in Papua New Guinea. It began at 00:03 on 16 June 2011 and concluded at 03:12 on 17 June 2011, spanning 27 hours and 8 minutes. During this interval, eight earthquakes were recorded, with magnitudes ranging from 4.8 to 6.4 and focal depths predominantly between 10 and 16 km, except for one event at 57 km.

This sequence exemplifies a typical earthquake swarm, characterized by clustered events without a dominant mainshock-aftershock pattern. Such swarms often arise from localized stress adjustments along fault systems or fluid migration within the crust, common in subduction-related environments.

Papua New Guinea occupies a tectonically complex zone within the Pacific Ring of Fire. The study area lies near the New Britain Trench, where the Solomon Sea Plate subducts beneath the South Bismarck Plate. This convergence drives frequent seismicity, with the overriding plate experiencing both shallow crustal earthquakes and deeper events associated with the subducting slab. The regional geology features volcanic arcs and thrust faults that accommodate oblique convergence, contributing to elevated seismic hazard.

Historical records indicate nine swarms in the vicinity since 1 January 2000. These occurred in the following years with the noted frequencies: one in 2000, one in 2003, two in 2005, three in 2006, and two in 2010. The 2011 swarm fits within this pattern of episodic clustering.

Several strong earthquakes have also struck the broader region since 2000. Notable events include a magnitude 7.0 quake 119 km east of Kimbe on 10 October 2018, located 23 km from the swarm center; a magnitude 7.5 event 131 km south-southwest of Kokopo on 5 May 2015, 89 km distant; a magnitude 7.0 shock 72 km east-southeast of Kimbe on 4 August 2010, 52 km away; a magnitude 7.3 earthquake in the New Britain region on 18 July 2010, 68 km from the center; and a magnitude 7.8 event 138 km south-southwest of Kokopo on 17 November 2000, 78 km distant. These demonstrate the area's capacity for large-magnitude ruptures along the plate interface.

The 2011 swarm's largest event reached magnitude 6.4 at 00:03:35 on 16 June, followed by magnitude 5.3 and 5.1 shocks within the first hour. Subsequent activity included additional magnitude 5+ events through 17 June, with most events at shallow depths conducive to felt shaking onshore. The temporal distribution showed an initial energetic phase tapering over the following day.

Such swarms provide valuable data for understanding stress transfer and fault interactions in subduction zones. Monitoring networks continue to track activity in this high-hazard setting, where cumulative strain release from both swarms and larger events shapes long-term seismic risk.

References

SeismoSight internal classification data for swarm parameters and historical statistics.
USGS Earthquake Catalog for regional tectonic framework and strong-event context.