Seismic Swarm VS20260429.1: Analysis of Activity Southwest of Volcano, Hawaii

A significant seismic swarm, designated VS20260429.1, was recorded 9 km southwest of Volcano, Hawaii, on the Big Island. The sequence began at 02:07 on 28 April 2026 and concluded at 21:12 on 7 May 2026, spanning 235 hours and 5 minutes. During this period, 120 earthquakes were detected, providing valuable data on subsurface dynamics in one of Earth's most active volcanic regions.

The swarm's first 100 events reveal predominantly low-magnitude activity. Magnitudes ranged from 0.6 to 2.4, with the majority between 1.4 and 1.8. Depths were mostly shallow, clustered between 0 and 10 km, consistent with processes in the volcanic edifice. Notable deeper events included magnitudes of 1.7 at 27 km on 29 April, 1.8 at 24 km on 29 April, and pairs reaching 2.0 and 1.7 near 28–29 km on 30 April. Later events on 4–5 May showed additional activity at 26–28 km. These patterns indicate both shallow crustal adjustments and possible deeper magmatic or tectonic influences.

Geologically, the location lies on the south flank of Kīlauea volcano within the Hawaiian hotspot chain. Kīlauea, one of the world's most active volcanoes, sits above a mantle plume that has built the Hawaiian Islands over millions of years. The island's southeast region experiences frequent seismicity due to magma transport through rift zones, gravitational spreading of the volcanic flank, and interactions with the underlying oceanic crust. Earthquake swarms here often precede or accompany eruptive episodes, as magma movement fractures rock and induces slip on faults.

Historical records show 118 swarms in the area since 2000, with notable increases in frequency during 2020 (12 swarms), 2023 (21 swarms), and 2024 (15 swarms). Earlier decades recorded fewer events, suggesting possible changes in monitoring sensitivity or volcanic behavior. Such swarms are typical of Kīlauea's East Rift Zone and summit caldera, where repeated intrusions maintain the volcano's dynamic state.

This swarm's characteristics align with established models of Hawaiian volcanism, where shallow events reflect brittle failure in the upper crust and deeper signals may trace magma pathways. Continued monitoring by the Hawaiian Volcano Observatory supports hazard assessment for nearby communities.

References

USGS Earthquake Catalog
Hawaiian Volcano Observatory reports
SeismoSight internal swarm database