Seismic Swarm S20110204.1: Analysis of Activity near Kilauea Volcano

Seismic swarm S20110204.1 occurred 6 km SSW of Volcano, Hawaii, on the Big Island. The sequence began at 13:57 on 3 February 2011 and concluded at 06:43 on 18 February 2011, spanning 352 hours and 46 minutes. During this interval, 387 earthquakes were recorded. The swarm was located in the seismically active zone associated with Kilauea volcano, part of the Hawaiian hotspot chain formed by the Pacific plate moving over a mantle plume.

Kilauea ranks among the world's most active volcanoes, with persistent summit and rift-zone eruptions driven by basaltic magma ascent. Earthquake swarms in this region commonly arise from magma intrusion into shallow dikes, hydrothermal fluid movement, or slip along pre-existing faults within the volcanic edifice. Depths in the provided events cluster between 0 and 7 km, consistent with the brittle-ductile transition zone beneath the summit and upper east rift. Occasional deeper events reaching 28–37 km reflect stress changes in the underlying oceanic crust or lower volcanic pile.

Analysis of the first 100 events reveals predominantly low-magnitude activity. Magnitudes ranged from 0.2 to 2.8, with the largest event (M 2.8) occurring on 4 February at 11:54. Most events registered below M 2.0, typical of volcanic swarms where energy release occurs through numerous small fractures rather than a single large rupture. Depths remained shallow for the majority, supporting an interpretation of near-surface magmatic or hydrothermal processes. A few outliers at greater depths suggest minor involvement of deeper structures but did not dominate the sequence.

Historical records indicate 25 swarms have occurred in the same area since 1 January 2000. Yearly counts show variability: three in 2000, one in 2001, eight in 2003, five in 2004, one each in 2005 and 2008, two in 2006, and four in 2007. This pattern underscores the recurrent nature of swarm activity tied to Kilauea’s ongoing volcanic and tectonic regime.

The 2011 swarm fits within the long-term behavior of the Kilauea system, where episodic intrusions produce dense clusters of small earthquakes without necessarily leading to immediate surface eruptions. Such sequences contribute to monitoring efforts that help forecast changes in volcanic unrest.

References

• USGS Hawaiian Volcano Observatory earthquake catalog (internal swarm classification S20110204.1)
• SeismoSight internal swarm database for event parameters and historical counts