Seismic Swarm PS20080719.1 Near Lata, Solomon Islands

On 19 July 2008, a seismic swarm designated PS20080719.1 was recorded approximately 134 km west-southwest of Lata in the Solomon Islands. The sequence began at 09:27 UTC and concluded at 11:45 UTC, encompassing six earthquakes over a span of two hours and eighteen minutes. All events occurred at shallow depths between 10 and 11 km, consistent with activity along the convergent margin in this segment of the western Pacific.

The sequence opened with a magnitude 6.6 earthquake at 09:27:01 UTC. Within seven minutes, a magnitude 5.5 event followed at 09:34:26 UTC. Subsequent shocks included a magnitude 5.0 at 10:35:38 UTC, a magnitude 6.2 at 11:01:17 UTC, and two magnitude 5.2 events at 11:15:24 UTC and 11:45:40 UTC. The temporal clustering and rapid succession of moderate-to-strong events characterize this swarm as a short-lived episode of elevated seismicity without a single dominant mainshock-aftershock pattern.

The Solomon Islands lie along the complex boundary between the Pacific Plate and the Australian Plate, where oblique subduction produces frequent moderate and large earthquakes. The Santa Cruz Islands region, in particular, experiences recurrent activity due to the interaction of multiple microplates and the presence of the San Cristobal Trench system. Shallow focal depths such as those observed in the 2008 swarm are typical of the upper plate and megathrust interface in this area.

Historical records maintained since 1 January 2000 indicate that only two prior swarms have been identified in the immediate vicinity: one in 2005 and another in 2007. This low frequency underscores the episodic nature of swarm activity relative to the more common isolated mainshock sequences in the region.

Several significant earthquakes have occurred nearby in the same period. A magnitude 7.0 event took place on 18 July 2015 roughly 80 km west-northwest of Lata. On 6 February 2013, a magnitude 7.1 shock struck 112 km west-southwest of Lata, while the magnitude 8.0 Santa Cruz Islands earthquake of the same date occurred 61 km from the 2008 swarm center. These larger events illustrate the persistent seismic hazard along this plate boundary.

The 2008 swarm provides a useful example of clustered shallow seismicity that can occur without producing a great earthquake, yet it highlights the ongoing tectonic strain accumulation in the Solomon Islands arc. Continued monitoring remains essential for understanding precursory patterns in this highly active subduction environment.

References
SeismoSight internal swarm catalogue PS20080719.1
USGS Earthquake Catalog (historical events)
Global CMT Project (moment-tensor solutions for regional events)