Seismic Swarm VS20030809.1: Analysis of Activity Near Volcano, Hawaii
An earthquake swarm designated VS20030809.1 was recorded 6 km south-southwest of Volcano, Hawaii, on the Big Island. The sequence began at 08:41 on 8 August 2003 and concluded at 23:04 on 15 August 2003, spanning 182 hours and 22 minutes. In total, 101 earthquakes were detected during this period.
The swarm occurred within the seismically active zone associated with Kilauea volcano, part of the Hawaiian hotspot chain. This region experiences frequent seismic swarms driven by magma movement, dike intrusions, and gravitational adjustments along the volcano's south flank. Depths for the majority of events ranged from 0 to 13 km, consistent with shallow crustal processes typical of Hawaiian volcanism, although isolated events reached depths of 30–48 km.
Analysis of the first 100 events reveals predominantly low-magnitude activity. Magnitudes ranged from 1.1 to 2.3, with most falling between 1.4 and 1.9. The largest event measured 2.3 and occurred on 11 August at a depth of 12 km. Temporal clustering was evident, with higher rates during daylight hours on 8–10 August and renewed bursts on 11 and 14 August. Depths remained shallow for the bulk of events, suggesting involvement of the volcanic edifice rather than deeper mantle sources.
Historical records since 1 January 2000 indicate eight comparable swarms in the same area. These occurred in 2000 (three swarms), 2001 (one swarm), and 2003 (four swarms, including the present sequence). Such recurrence aligns with ongoing magmatic and tectonic processes at Kilauea, where swarms often precede or accompany eruptive episodes.
The 2003 swarm exhibited classic characteristics of volcanic seismicity, including tight spatial clustering and a lack of a single dominant mainshock. Event rates peaked early in the sequence before gradually declining, a pattern commonly linked to fluid migration or stress relaxation within the volcanic system.
- SeismoSight internal swarm classification VS20030809.1
- USGS Hawaiian Volcano Observatory seismic catalogs (2000–2003)