Seismic Swarm S20241102.1 Near Naalehu, Hawaii

A seismic swarm designated S20241102.1 was recorded 42 km east-southeast of Naalehu on Hawaii’s Big Island. The sequence began at 04:54 on 2 November 2024 and concluded at 16:28 on 4 November 2024, spanning 59 hours and 34 minutes. During this interval, 59 earthquakes were registered.

The events clustered at shallow depths between 4 km and 13 km, with the majority occurring between 9 km and 11 km. Magnitudes ranged from 1.3 to 4.3. The largest shock, magnitude 4.3, struck at 22:05 on 2 November at a depth of 5 km. Other notable events included a magnitude 3.9 at 09:49 on 2 November (11 km depth) and a magnitude 3.8 at 00:33 on 3 November (10 km depth). Activity showed two distinct peaks on 2 November, followed by a gradual decline through 4 November.

This swarm occurred within the tectonically active south flank of Kilauea volcano. The region experiences frequent seismicity driven by magma movement, gravitational spreading of the volcanic edifice, and slip along the basal decollement fault. Depths recorded in the swarm align with the typical range for both volcanic-tectonic and shallow crustal events in this sector.

Since 1 January 2000, six comparable swarms have been documented in the same area: one each in 2001, 2005, 2017, and 2020, and two in 2021. These episodes illustrate the recurring nature of clustered seismicity linked to ongoing volcanic and flank dynamics.

The November 2024 swarm fits the established pattern of short-duration, moderate-magnitude sequences that release strain without producing significant surface deformation or eruptive activity. Continued monitoring remains essential given the proximity to populated coastal communities and the potential for larger flank earthquakes.

References

• SeismoSight internal swarm classification S20241102.1
• Hawaiian Volcano Observatory seismic catalogs (historical swarm records)