Seismic Swarm VS20031119.1: Analysis of Activity Near Volcano, Hawaii

A notable earthquake swarm designated VS20031119.1 occurred 6 km southwest of Volcano, Hawaii, from 19:29 on 18 November 2003 to 15:50 on 22 November 2003. Over this 92-hour period, 64 earthquakes were recorded, providing valuable data on subsurface dynamics in one of Earth's most active volcanic regions.

The swarm exhibited typical characteristics of volcanic seismicity, with event magnitudes ranging from 1.3 to 2.3. Depths varied between 0 km and 13 km, indicating activity across shallow crustal layers. Early events on 18 November included magnitudes of 2.2 at 9 km depth and 2.0 at 5 km, followed by a cluster on 19 November featuring multiple 2.1–2.2 magnitude quakes at depths of 4–12 km. Activity persisted through 20–21 November with consistent low-to-moderate magnitudes and depths mostly between 4 km and 10 km, concluding with smaller events around 1.3–1.9 on 22 November at similar depths.

This pattern reflects episodic stress release likely tied to fluid migration or minor magma movement beneath the surface. Swarms of this type differ from tectonic mainshock-aftershock sequences by their lack of a dominant event and relatively uniform magnitude distribution, offering insights into the pressurized hydrothermal systems common in Hawaii.

The Volcano area lies on the Big Island within the Hawaiian volcanic chain, formed by the Pacific Plate's passage over a persistent mantle hotspot. This tectonic setting drives ongoing shield volcano growth, particularly at nearby Kilauea and Mauna Loa, where magma ascent generates frequent microseismicity. Depths recorded in the swarm align with known brittle-ductile transition zones in the volcanic edifice, where temperatures and pressures facilitate small ruptures.

Historical records since 1 January 2000 document nine swarms in the region, with three in 2000, one in 2001, and five in 2003. These recurrent episodes underscore the persistent volcanic influence on local seismicity, aiding long-term hazard assessment for nearby communities.

Overall, swarm VS20031119.1 exemplifies the dynamic interplay between hotspot volcanism and crustal stresses, contributing to refined models of Hawaiian seismic behavior.

References

SeismoSight internal swarm classification records USGS Hawaiian Volcano Observatory geological summaries