Seismic Swarm PS20050306.2: Activity Near Kirakira, Solomon Islands

On 6 March 2005, a seismic swarm designated PS20050306.2 occurred approximately 140 km east-southeast of Kirakira in the Solomon Islands. The sequence began at 01:39 local time and concluded at 17:37 the same day, spanning 15 hours and 58 minutes. During this interval, six earthquakes were recorded, with magnitudes ranging from 4.3 to 6.1 and focal depths predominantly at 10 km, except for one event at 60 km.

The events unfolded in rapid succession. The initial pair occurred within seconds of each other at 01:39, registering magnitudes of 5.9 and 5.4. A stronger event of magnitude 6.1 followed at 04:39. Later activity included a magnitude 4.3 shock at 14:35, a magnitude 5.6 event at 14:59, and a final magnitude 5.2 earthquake at 17:37. This clustering of moderate-magnitude quakes within a confined timeframe exemplifies typical swarm behavior in tectonically active zones.

The Solomon Islands occupy a complex tectonic setting along the convergent boundary between the Pacific and Australian plates. Subduction processes drive frequent seismicity throughout the region, which forms part of the Pacific Ring of Fire. Historical records since 2000 indicate only two prior swarms in the immediate area, occurring in 2002 and 2004. Stronger individual earthquakes have also struck nearby, including a magnitude 7.0 event on 9 November 2004 located 82 km from the swarm center and a magnitude 7.6 earthquake on 12 April 2014 situated 96 km away.

Such swarms provide valuable data on stress distribution along subduction interfaces. The shallow depths of most events in this sequence suggest activation within the upper crustal layers influenced by plate convergence. Ongoing monitoring by regional seismic networks continues to track patterns that inform hazard assessment for the Solomon Islands archipelago.

References

SeismoSight internal swarm classification records
USGS Earthquake Catalog (historical events 2000–2014)
Global tectonic summaries from the Incorporated Research Institutions for Seismology (IRIS)