Seismic Swarm VS20041103.1: Analysis of Activity Near Volcano, Hawaii

Seismic swarms represent clusters of earthquakes occurring in rapid succession within a localized area, often linked to magmatic or hydrothermal processes in volcanic regions. The swarm designated VS20041103.1 was recorded 8 km west-southwest of Volcano, Hawaii, beginning at 08:20 on 2 November 2004 and concluding at 10:14 on 3 November 2004. Over this 25-hour, 53-minute period, 30 earthquakes were detected, with magnitudes ranging from 1.0 to 2.2 and focal depths between 1 and 7 km.

Event Characteristics and Temporal Patterns

The sequence initiated with a magnitude 1.4 event at 1 km depth. Subsequent activity showed clustering, particularly between 22:41 on 2 November and 02:56 on 3 November, when the majority of events occurred. Peak magnitudes included a 2.2 event at 4 km depth at 00:55:43 on 3 November, accompanied by several 1.6–1.9 events at 2–4 km depths. Later events tapered off, ending with two magnitude 1.1 quakes at 1 km depth. Depths remained predominantly shallow (1–4 km), consistent with upper-crustal processes, though one outlier reached 7 km.

This distribution suggests episodic energy release, potentially driven by fluid migration or minor crustal adjustment in a tectonically active volcanic setting. No single dominant mainshock was evident; instead, the events displayed swarm-like behavior with comparable magnitudes throughout.

Geological Context of the Region

The location lies on the Big Island of Hawaii, within the influence of the Hawaiian hotspot. This volcanic chain results from the Pacific Plate moving over a mantle plume, producing shield volcanoes such as Kilauea and Mauna Loa. The area near Volcano sits amid active rift zones and flank structures where magma ascent and storage frequently induce seismicity. Historical monitoring by the Hawaiian Volcano Observatory has documented recurrent earthquake swarms tied to dike intrusions, summit inflation, and rift-zone propagation.

Since 2000, 15 such swarms have occurred in the broader region, with notable concentrations in 2003 (8 events) and additional activity in 2000 (3), 2001 (1), and 2004 (3). These episodes underscore the persistent volcanic dynamism of the southeast flank of Kilauea and adjacent areas, where shallow seismicity often precedes or accompanies surface deformation.

Implications for Volcanic Monitoring

Shallow focal depths in VS20041103.1 align with typical patterns observed during magma movement at depths of a few kilometers. Such swarms provide valuable data for assessing unrest levels, though this particular sequence remained modest in magnitude and did not culminate in eruptive activity. Continued integration of seismic records with geodetic and gas-emission measurements enhances understanding of subsurface dynamics in hotspot settings.

References

• USGS Hawaiian Volcano Observatory reports on Kilauea seismicity (2000–2004).
• ANSS Comprehensive Earthquake Catalog for event parameters.
• Geological Society of America summaries of Hawaiian hotspot volcanism.