Seismic Swarm S20240602.2: Activity Southwest of Volcano, Hawaii

A seismic swarm designated S20240602.2 was recorded southwest of Volcano, Hawaii, beginning at 00:52 on 2 June 2024 and concluding at 17:41 on 11 June 2024. Over 232 hours and 49 minutes, the sequence produced 450 earthquakes. The events clustered approximately 7 km southwest of the town of Volcano on the Island of Hawaii, an area overlying the active Kilauea volcanic system.

Analysis of the first 100 events reveals predominantly shallow seismicity. Magnitudes ranged from 0.5 to 3.0, with the largest reaching 3.0 on 3 June at 01:11:18. Depths were concentrated between 0 and 2 km, though one event occurred at 6 km. Early activity on 2 June included pairs of nearly simultaneous events, such as two at 00:52:20 with magnitudes 1.7 and 2.3. Later clusters on the evening of 2 June featured multiple events exceeding magnitude 2.5 within minutes, including successive shocks at 22:08–22:28. By early 3 June, the sequence maintained a steady rate with magnitudes mostly between 1.7 and 2.6.

This swarm occurred within the well-documented volcanic and tectonic setting of Kilauea. The Hawaiian Islands form above a mantle hotspot, where magma ascent drives both eruptive and intrusive processes. Kilauea’s south flank and summit regions regularly experience earthquake swarms linked to magma migration along rift zones or pressure changes within the shallow plumbing system. Such swarms have been a recurring feature of the volcano’s behavior for decades.

Historical records maintained since 2000 document 111 swarms in the broader region. Annual counts show notable variation, with peaks in 2023 (21 swarms), 2020 (13), and 2018 (10). Lower activity occurred in several years, including only one swarm each in 2001, 2005, 2008, and 2013. The 2024 total reached six swarms by mid-year, placing the current sequence within an elevated period of swarm frequency compared with earlier decades.

Seismic swarms at Kilauea often accompany or precede changes in volcanic unrest, though many remain non-eruptive. Depths in the 0–2 km range align with the shallow magma storage and transport zones beneath the volcano’s flanks. Continued monitoring of event rates, magnitudes, and any migration of hypocenters provides key indicators for assessing whether magma movement is accelerating toward the surface.

The S20240602.2 swarm adds to the extensive catalog of seismic activity that characterizes Hawaii’s dynamic geology. Its timing, location, and event statistics fit established patterns associated with Kilauea’s persistent volcanic environment.