Seismic Swarm S20070704.1: Analysis of Activity South of Volcano, Hawaii

The seismic swarm designated S20070704.1 occurred 8 km south of Volcano, Hawaii, on the Big Island. This region lies on the southern flank of Kilauea volcano, part of the Hawaiian hotspot chain where the Pacific plate moves over a mantle plume. Kilauea remains one of the world's most active volcanoes, with frequent magma intrusions that generate seismic swarms through rock fracturing and fluid movement.

The swarm initiated at 23:15 on 3 July 2007 and concluded at 13:36 on 22 July 2007, spanning 446 hours and 21 minutes. In total, 216 earthquakes were recorded. Such swarms are characteristic of the area, reflecting ongoing volcanic and tectonic processes along rift zones and flank faults.

Historical records since 1 January 2000 document 21 swarms in the vicinity. These occurred in the following yearly totals: three in 2000, one in 2001, eight in 2003, four in 2004, one in 2005, two in 2006, and two in 2007. This pattern underscores the recurrent nature of clustered seismicity tied to Kilauea's dynamic magmatic system.

Examination of the first 100 events reveals predominantly low-magnitude activity. Magnitudes ranged from 0.8 to 2.6, with the majority falling between 1.0 and 2.0. Depths remained shallow, concentrated between 0 and 10 km, consistent with volcanic seismicity rather than deeper tectonic sources. Early events on 4 July clustered tightly in time, with repeated magnitudes near 1.4–1.9 at depths of 1–2 km. Subsequent days showed a gradual increase in slightly deeper events, including isolated shocks at 25 km and 10 km, while most stayed within 5 km. Temporal distribution indicated bursts of activity separated by quieter intervals, typical of magma-driven swarms.

Overall, the sequence aligns with expected behavior in this volcanically active setting. Shallow focal depths and modest magnitudes point to processes such as dike propagation or pressurization beneath the surface. No events exceeded magnitude 3, limiting potential for significant surface impact.

Data source: SeismoSight internal classification for swarm parameters and event details. Geological context drawn from standard references on Hawaiian volcanism.