Seismic Swarm S20000425.1: Analysis of Activity South of Volcano, Hawaii
Seismic swarm S20000425.1 was recorded 16 km south of Volcano, Hawaii, on the Big Island. The sequence began at 10:17 on 24 April 2000 and concluded at 09:09 on 27 April 2000, spanning 70 hours and 51 minutes. During this interval, 63 earthquakes were detected.
This swarm occurred within the seismically active south flank of Kilauea volcano. The Hawaiian Islands formed through prolonged volcanic activity driven by a mantle hotspot beneath the Pacific Plate. Kilauea, one of the world's most active volcanoes, features frequent shallow seismicity linked to magma movement, flank deformation, and faulting along the Hilina fault system. Earthquake swarms in this region commonly reflect stress adjustments associated with volcanic processes rather than tectonic plate boundaries.
Magnitudes in the swarm ranged from 0.6 to 2.8, with the largest event measuring 2.8 at a depth of 7 km on 25 April at 09:02. Most events clustered between magnitudes 1.5 and 2.2. Focal depths predominantly fell between 4 km and 11 km, consistent with activity in the volcanic crust beneath the south flank. A smaller number of shallower events occurred near 1–3 km, while a few reached 11 km.
Temporal distribution showed peak activity during the first 24 hours, with multiple events per hour on 24–25 April. Activity gradually declined over the following days, ending with isolated smaller events on 27 April. No events exceeded magnitude 3.0, indicating a low-energy swarm typical of Kilauea's background unrest.
Such swarms contribute to monitoring volcanic hazard levels. The 2000 sequence aligns with patterns observed in Kilauea's long-term record of episodic seismic bursts tied to magma intrusion or flank slip. Since 1 January 2000, this event represents the sole recorded swarm in the internal classification, underscoring its distinct occurrence within the early monitoring period.
Geological context for the area includes young basaltic lava flows and ongoing ground deformation. Reliable sources confirm Kilauea's persistent activity through the present day, with the south flank remaining a focus for both seismic and geodetic observation.
References
USGS Hawaiian Volcano Observatory reports on Kilauea seismicity.
Hawaii Volcanoes National Park geological summaries.
SeismoSight internal swarm classification records.