Seismic Swarm PS20180329.1 East of Kimbe, Papua New Guinea

On 29 March 2018, a seismic swarm designated PS20180329.1 was recorded approximately 159 km east of Kimbe in Papua New Guinea. The sequence began at 07:30 and concluded at 22:51 local time, encompassing eight earthquakes over 15 hours and 20 minutes. This event occurred within the tectonically complex Bismarck Sea region, where multiple plate boundaries converge.

The swarm initiated with a magnitude 5.0 earthquake at a depth of 126 km. Activity intensified later that evening, featuring a magnitude 6.9 event at 35 km depth at 21:25. Subsequent shocks included magnitudes of 5.3, 4.6, 5.1, 5.0, 5.0, and 5.7, with depths ranging from 10 km to 80 km. These varying focal depths suggest activation along both shallow crustal faults and deeper subduction-related structures.

Papua New Guinea lies at the northern margin of the Australian Plate, where it interacts with the Pacific Plate and several microplates. The area east of Kimbe is influenced by the New Britain subduction zone, which accommodates oblique convergence and generates frequent intermediate-depth seismicity. Historical records indicate persistent seismic productivity in this setting, driven by slab dehydration and stress transfer across the plate interface.

Since 2000, the region has experienced 23 documented swarms. These occurred in 2000 (six events), 2003 (one), 2005 (two), 2006 (three), 2010 (two), 2011 (one), 2013 (one), 2014 (one), 2015 (five), and 2016 (one). Such episodic clustering reflects the region's capacity for distributed strain release rather than isolated mainshock-aftershock sequences.

Notable larger earthquakes have also struck nearby. A magnitude 7.0 event occurred 119 km east of Kimbe on 10 October 2018, 56 km from the swarm center. Earlier, a magnitude 7.5 shock on 5 May 2015 was located 131 km south-southwest of Kokopo, 37 km from the swarm epicenter. The largest recent event, magnitude 7.8 on 17 November 2000, struck 138 km south-southwest of Kokopo, 30 km from the swarm location. These events underscore the potential for both swarm activity and isolated great earthquakes along the same tectonic corridor.

Insights from the 2018 swarm highlight the role of fluid migration and stress perturbations in triggering clustered seismicity at multiple depths. Continued monitoring remains essential given the proximity of population centers on New Britain Island to these active structures.

References:
SeismoSight internal swarm catalog PS20180329.1
USGS Earthquake Catalog (regional tectonics summaries)