Seismic Swarm S20260120.2: Analysis of Recent Activity Near Volcano, Hawaii

A seismic swarm designated S20260120.2 occurred 5 km southwest of Volcano, Hawaii, on the Big Island. The sequence began at 12:58 on 19 January 2026 and concluded at 04:57 on 21 January 2026, lasting 39 hours and 59 minutes. During this period, 29 earthquakes were recorded, with magnitudes ranging from 0.5 to 1.9 and focal depths predominantly between 0 and 2 km, except for one event at 6 km depth. All events remained below magnitude 2.0, indicating low-energy volcanic or tectonic processes typical of the area.

The swarm exhibited clustered activity, with 14 events on 19 January concentrated in the afternoon and evening hours, followed by 13 on 20 January and a final small event early on 21 January. Shallow depths suggest involvement of near-surface structures associated with volcanic flanks rather than deeper tectonic sources. Such patterns align with magma movement or fluid migration beneath the Kilauea volcanic system.

The Volcano region lies on the southeast flank of Kilauea, one of the world's most active shield volcanoes fed by the Hawaiian hotspot. This tectonic setting produces frequent shallow seismicity from volcanic inflation, dike intrusions, and gravitational spreading of the volcanic edifice. Historical monitoring by the USGS Hawaiian Volcano Observatory shows that seismic swarms often precede or accompany eruptive episodes, though not all swarms culminate in surface activity. Kilauea’s summit caldera and rift zones host persistent microseismicity driven by the interaction between rising magma and the overlying crust.

Since 2000, 121 seismic swarms have been documented in the region, with notable increases in frequency during 2023 (21 swarms) and 2024 (16 swarms). Earlier decades recorded fewer events, such as three in 2000 and nine in 2018. This uptick may reflect enhanced monitoring sensitivity or changes in volcanic unrest patterns. The 2018 lower East Rift Zone eruption demonstrated how prolonged swarms can signal significant magma transport, underscoring the value of continuous surveillance.

No surface deformation or eruptive signs accompanied the January 2026 swarm, consistent with many prior low-magnitude sequences. Continued observation remains essential given Kilauea’s history of sudden activity shifts. Residents and visitors should follow guidance from the Hawaiian Volcano Observatory and Hawaii Volcanoes National Park for any updates on volcanic conditions.

References

USGS Hawaiian Volcano Observatory – Kilauea activity summaries and earthquake catalogs.
Hawaii Volcanoes National Park geological resources on volcanic processes.
Global Volcanism Program, Smithsonian Institution – Kilauea eruption history.