Seismic Swarm VS20040113.1 Near Volcano, Hawaii

The seismic swarm VS20040113.1 occurred in the volcanic region of Hawaii's Big Island, approximately 7 km southwest of the town of Volcano. This event unfolded over 18 hours and 57 minutes, beginning at 14:19 on 12 January 2004 and concluding at 09:16 on 13 January 2004. A total of 25 earthquakes were recorded during this period, with magnitudes ranging from 1.4 to 2.2 and focal depths between 0 and 11 km.

The sequence began with a magnitude 1.9 event at a depth of 0 km on 12 January at 14:19:06. Subsequent activity included events such as a magnitude 2.0 quake at 11 km depth later that evening and several magnitude 1.9–2.1 events clustered around 07:00–09:00 on 13 January, many at depths of 7–11 km. The final recorded event was a magnitude 1.9 earthquake at 8 km depth. These shallow to intermediate depths align with typical patterns in Hawaii's volcanic systems, where seismicity often reflects stress changes in the crust.

Geologically, the area lies within the influence of the Hawaiian hotspot, a mantle plume responsible for the formation of the Hawaiian-Emperor seamount chain over millions of years. The Big Island hosts active shield volcanoes, including Kilauea, whose summit and rift zones experience frequent intrusive activity. Magma movement through dikes and reservoirs commonly triggers earthquake swarms as rock fractures under pressure. Depths of 0–11 km correspond to the brittle upper crust overlying the volcanic edifice, where such events are well-documented.

Historically, the region has recorded multiple swarms since 2000. Data indicate 12 swarms in total during this interval, distributed as three in 2000, one in 2001, and eight in 2003. These episodes underscore the persistent volcanic unrest characteristic of Kilauea's flank and summit areas, where swarms often precede or accompany eruptive phases driven by the hotspot's ongoing magma supply.

This swarm provides insight into localized seismic clustering, with most events exhibiting magnitudes below 2.2 and a concentration of activity in the later hours. Such patterns are consistent with fluid-induced fracturing in volcanic environments rather than tectonic plate boundary faulting.

References
Hawaiian Volcano Observatory, USGS Volcano Hazards Program
USGS Earthquake Catalog (Hawaii region summaries)
Global Volcanism Program, Smithsonian Institution (Hawaiian hotspot reports)