Seismic Swarm S20241201.2 Near Volcano, Hawaii: Analysis and Regional Context

Seismic swarm S20241201.2 occurred 7 km south of Volcano, Hawaii, on the Big Island. The sequence began at 05:04 on 30 November 2024 and concluded at 09:08 on 10 December 2024, spanning 244 hours and 3 minutes. During this period, 124 earthquakes were recorded. Analysis of the first 100 events shows magnitudes ranging from 0.3 to 3.0, with the majority between 1.5 and 2.5. Depths clustered predominantly between 0 and 5 km, though several events reached 28–40 km, indicating both shallow crustal and deeper magmatic influences.

The swarm exhibited typical characteristics of volcanic seismicity, with clusters of similar-magnitude events occurring in rapid succession. Notable activity included a 3.0 magnitude earthquake at 23:19 on 30 November and multiple 2.4–2.6 events on 3 and 4 December. Shallow events dominated early phases, while deeper occurrences appeared later in the sequence.

Hawaii’s geology is dominated by hotspot volcanism. The Big Island sits above the Hawaiian hotspot, where magma rises through the Pacific plate. Kilauea, located immediately north of the swarm epicenter, is one of the world’s most active volcanoes. Its south flank experiences frequent earthquake swarms due to magma intrusion along rift zones and gravitational spreading of the volcanic edifice. These swarms often precede or accompany eruptive episodes, reflecting stress changes from dike propagation.

Historical records indicate persistent seismic swarms in the region. Since 2000, 98 swarms have been documented near Volcano. Annual counts vary, with notable increases in 2003 (8), 2018 (9), 2023 (19), and 2024 (8). This pattern aligns with Kilauea’s episodic activity, including the 2018 lower Puna eruption and subsequent summit collapse, which altered stress regimes and increased swarm frequency.

Such swarms provide critical data on magma movement. Depths under 5 km typically signal shallow intrusions, while deeper events may reflect pressure changes in the summit reservoir or south flank décollement. Monitoring by the U.S. Geological Survey’s Hawaiian Volcano Observatory integrates these observations with deformation and gas measurements to assess eruption potential.

The December 2024 swarm fits within established patterns of Kilauea unrest. No surface eruption was associated with this sequence, consistent with many past swarms that dissipate without reaching the surface. Continued observation remains essential given the volcano’s dynamic nature.

References

SeismoSight internal classification records for swarm S20241201.2.
USGS Hawaiian Volcano Observatory volcanic activity summaries.
Global Volcanism Program, Smithsonian Institution – Kilauea reports.