Seismic Swarm S20110223.1: Analysis of Activity near Kilauea Volcano, Hawaii

The seismic swarm designated S20110223.1 occurred 7 km south of Volcano, Hawaii, on the Big Island. It began at 21:42 on 22 February 2011 and concluded at 21:44 on 27 February 2011, spanning 120 hours and 1 minute. During this interval, 117 earthquakes were recorded. This event aligns with the well-documented pattern of seismic swarms associated with Kilauea, one of the world’s most active shield volcanoes.

Kilauea forms part of the Hawaiian hotspot chain, where magma rises through the Pacific Plate, producing frequent eruptions and associated seismicity. The volcano’s summit caldera and East Rift Zone are primary sources of activity. Earthquakes in this region typically result from magma intrusion, rock fracturing, and gravitational settling along fault structures. Depths commonly range from surface levels to approximately 10 km, though deeper events can occur during significant unrest.

Analysis of the first 100 events in the swarm reveals predominantly shallow foci, with most occurring between 0 and 10 km depth. Magnitudes stayed low, generally below 2.0, consistent with volcanic rather than tectonic origins. Notable outliers included a magnitude 3.2 event at 1 km depth on 23 February at 15:00:06 and a magnitude 2.5 shock at 1 km on 24 February at 12:24:59. These shallow, low-magnitude sequences indicate fluid movement and minor fracturing within the volcanic edifice rather than large-scale fault rupture.

Historical records since 2000 show 24 comparable swarms in the area. Yearly counts include three in 2000, one in 2001, eight in 2003, four in 2004, one each in 2005 and 2006, four in 2007, one in 2008, and one in 2011. Such recurrence underscores the persistent volcanic dynamics of Kilauea, where swarms often precede or accompany eruptive episodes along rift zones.

The February 2011 swarm fits within this established framework of episodic unrest. Its brief duration and modest energy release reflect typical background behavior at this highly active volcanic center.

References

USGS Hawaiian Volcano Observatory reports on Kilauea seismicity.
Hawaii Volcanoes National Park geological summaries.
SeismoSight internal swarm classification database.