Earthquake Swarm PS20250210.1 Near Port-Vila, Vanuatu

A seismic swarm designated PS20250210.1 was recorded 66 km west-northwest of Port-Vila, Vanuatu, on 10 February 2025. The sequence began at 00:09 local time and concluded at 12:22, spanning 12 hours and 12 minutes. During this interval, five earthquakes were registered, with magnitudes ranging from 4.4 to 5.9 and focal depths between 10 km and 35 km.

The largest event reached magnitude 5.9 at a depth of 18 km shortly after the swarm onset. Subsequent shocks of magnitude 5.3 occurred at shallow depths of 10 km within the following seven minutes. Later activity included a magnitude 5.0 event at 10 km depth and a final magnitude 4.4 shock at 35 km depth. All events clustered tightly in both time and space, consistent with swarm behavior rather than a typical mainshock-aftershock sequence.

Vanuatu lies along the convergent boundary between the Australian and Pacific plates, where the Pacific plate subducts westward beneath the Australian plate at rates exceeding 10 cm per year. This subduction produces the New Hebrides Trench and an associated volcanic arc, rendering the region one of the most seismically active on Earth. Shallow to intermediate-depth earthquakes occur frequently due to plate interface slip, intraslab deformation, and upper-plate faulting.

Since 2000, eighteen earthquake swarms have been documented in the vicinity, occurring in 2002 (two swarms), 2004, 2005, 2009 (three), 2010, 2011 (three), 2012, 2015, 2016, 2018, 2020, 2021, and 2024. These episodes illustrate the episodic nature of clustered seismicity along the arc. Several major earthquakes have also struck nearby, including a magnitude 7.3 event 24 km west-northwest of Port-Vila on 17 December 2024, a magnitude 7.1 shock 125 km west of the capital in February 2012, two magnitude 7.3 events in August 2010 within 23–29 km of the swarm center, and a magnitude 7.2 earthquake 50 km west-northwest of Port-Vila in January 2002. The current swarm center lies within 14–80 km of these historical rupture zones, underscoring persistent strain accumulation and release along the plate interface.

Such swarms typically arise from fluid migration, aseismic slip, or stress triggering within the subduction complex. While individual events in the February 2025 sequence remained below damaging thresholds, their occurrence highlights the ongoing tectonic loading that can precede larger earthquakes. Continued monitoring is essential given Vanuatu’s high seismic hazard and the proximity of population centers to active fault segments.

References

SeismoSight internal swarm classification PS20250210.1
USGS Earthquake Catalog (historical events since 2000)
Global CMT Project (plate boundary parameters)