Seismic Swarm PS20221122.1 Southwest of Malango, Solomon Islands

A significant earthquake swarm, designated PS20221122.1, occurred 18 km southwest of Malango in the Solomon Islands. The sequence began at 02:03 on 22 November 2022 and concluded at 07:13 on 23 November 2022, spanning 29 hours and 10 minutes. During this period, 12 earthquakes were recorded, beginning with a magnitude 7.0 event at 14 km depth. Subsequent events included magnitudes of 5.5, 5.6, 5.4, 5.0, 6.0, 5.0, 5.0, 5.1, 5.1, 5.2, and 5.0, with most hypocenters at approximately 10 km depth.

This swarm provided insight into clustered seismic behavior in the region. The initial magnitude 7.0 shock at 02:03:06 triggered a rapid succession of moderate aftershocks within the first hour, including a magnitude 6.0 event at 02:37:57. Activity then tapered but persisted with smaller events through the following day, culminating in a magnitude 5.0 shock at 07:13:51 on 23 November. Depths remained shallow, consistent with upper-crustal faulting.

The Solomon Islands occupy a tectonically complex zone within the Pacific Ring of Fire, where the Pacific Plate subducts beneath the Australian Plate along the Solomon Trench. This convergence produces frequent shallow to intermediate-depth earthquakes and associated volcanic arcs. Historical records since 2000 indicate only two prior swarms in the immediate area—one in 2010 and another in 2016—highlighting the relative rarity of such clustered sequences compared to isolated mainshock-aftershock patterns.

The 22 November 2022 magnitude 7.0 event stands as the strongest recorded near Malango since 2000. Its proximity to the swarm centroid underscores ongoing strain release along local fault systems influenced by regional plate motion.

References
SeismoSight internal swarm classification PS20221122.1
USGS Earthquake Catalog (regional tectonics summary)