Seismic Swarm PS20130131.1: Analysis of Activity Near Lata, Solomon Islands

The seismic swarm designated PS20130131.1 occurred in a tectonically active region 63 km east-northeast of Lata, Solomon Islands. This event sequence began at 23:03 on 30 January 2013 and concluded at 06:42 on 31 January 2013, spanning 7 hours and 38 minutes. During this interval, seven earthquakes were recorded, with magnitudes ranging from 5.1 to 6.1 and focal depths predominantly between 9 and 46 km.

The sequence initiated with a magnitude 6.1 event at 23:03:43 on 30 January at a depth of 10 km. Subsequent activity included another magnitude 6.1 quake at 03:33:43 on 31 January (9 km depth), followed by a magnitude 5.8 event at 03:57:56 (10 km depth). Later shocks comprised a magnitude 5.1 at 05:16:56 (11 km depth), magnitude 5.5 at 05:18:09 (10 km depth), magnitude 5.3 at 06:42:06 (10 km depth), and a final magnitude 5.1 at 06:42:13 (46 km depth). These events clustered tightly in both time and space, characteristic of swarm behavior without a dominant mainshock-aftershock pattern.

The Solomon Islands occupy a complex convergent margin along the Pacific Ring of Fire, where the Pacific Plate subducts beneath the Australian Plate. This setting produces frequent seismic activity, including swarms and larger thrust events. The Temotu Province around Lata experiences elevated seismicity due to interactions involving the Solomon Sea microplate and regional fault systems. Historical records indicate persistent tectonic strain accumulation and release in this area.

Since 2000, five prior swarms have been documented in the region, occurring in 2000, 2004, 2007, 2009, and 2012. Each involved limited event counts similar to the 2013 sequence. Following PS20130131.1, two notable earthquakes occurred nearby: a magnitude 7.1 event on 8 February 2013 located 32 km southeast of Lata (approximately 54 km from the swarm center) and a magnitude 7.0 event on 6 February 2013 situated 33 km northwest of Lata (about 88 km from the swarm center). These larger shocks highlight the ongoing potential for significant rupture in adjacent segments.

Such swarms provide insight into precursory stress migration within subduction zones. The shallow depths of most events in PS20130131.1 suggest activation along upper-plate structures or the plate interface, consistent with regional tectonics. Continued monitoring remains essential given the area's history of clustered seismicity.

References
United States Geological Survey Earthquake Catalog
Global Centroid Moment Tensor Project
SeismoSight internal swarm classification records