Seismic Swarm PS20070902.1: Analysis of September 2007 Activity near Lata, Solomon Islands

A seismic swarm designated PS20070902.1 was recorded 95 km south of Lata in the Solomon Islands. The sequence began at 01:05 on 2 September 2007 and concluded at 01:28 on 3 September 2007, encompassing 12 earthquakes over 24 hours and 23 minutes. The events clustered at depths of approximately 35–51 km, with magnitudes ranging from 4.8 to 7.2.

The swarm initiated with a magnitude 7.2 earthquake at 01:05:18 on 2 September, followed by a series of aftershocks. Subsequent events included two magnitude 5.0 quakes within the first hour, a magnitude 5.4 at 02:34, and a magnitude 6.3 at 02:35. Further activity continued throughout the day with additional events of magnitude 5.1–5.4, culminating in a final magnitude 5.1 shock at 01:28 on 3 September. All but one event occurred at 35–36 km depth, with the closing shock at 51 km.

The Solomon Islands lie along the convergent boundary between the Pacific and Australian plates, forming part of the Pacific Ring of Fire. Subduction of the Australian Plate beneath the Pacific Plate drives intense seismic activity in this region. The area near Lata experiences frequent moderate to large earthquakes due to this tectonic interaction, with historical records showing repeated swarm-like sequences.

Since 1 January 2000, three prior swarms have been documented in the vicinity: one each in 2000, 2004, and 2006. Strong earthquakes recorded in the broader area during this period include a magnitude 7.1 event 32 km southeast of Lata on 8 February 2013, a magnitude 7.8 event 196 km northwest of Sola, Vanuatu, on 7 October 2009, and the magnitude 7.2 shock of 2 September 2007 itself, located 37 km from the swarm center.

This swarm exemplifies the episodic clustering typical of subduction-zone settings, where stress release along the plate interface produces both isolated large events and dense aftershock sequences. Depths in the 35–50 km range align with the expected seismogenic zone for this margin.

References

SeismoSight internal swarm classification PS20070902.1
USGS Earthquake Catalog (regional tectonics and historical events)