Seismic Analysis of Swarm VS20081205.1 Near Volcano, Hawaii

The earthquake swarm designated VS20081205.1 occurred 7 km southwest of Volcano, Hawaii, on the Big Island. This region lies within the active volcanic zone associated with Kilauea, one of the world's most active shield volcanoes. Seismic activity here primarily results from magma intrusion, flank movement, and crustal adjustments linked to ongoing volcanic processes. The swarm commenced at 18:24 on 4 December 2008 and concluded at 21:59 on 1 January 2009, spanning 675 hours and 34 minutes with a total of 473 recorded events.

Examination of the first 100 events reveals predominantly low-magnitude earthquakes, with values ranging from 0.9 to 3.4. The majority clustered between 1.0 and 2.0, indicating microseismic activity typical of volcanic swarms. Depths remained shallow, concentrated between 0 and 10 km, consistent with near-surface magmatic or hydrothermal interactions. Temporal distribution showed initial sparse occurrences on 4 December, followed by increased frequency on 5 and 6 December, including several events above magnitude 2.0. A notable peak included a magnitude 3.4 event on 7 December at 8 km depth. Subsequent days through 9 December exhibited continued but declining rates, with events often occurring in tight temporal clusters separated by brief lulls.

This pattern aligns with known volcanic seismicity in the area, where swarms frequently accompany subtle ground deformation or gas emissions without leading to immediate eruptions. Depths near zero suggest possible involvement of surface or very shallow sources, while deeper events up to 10 km point to connections with the volcanic plumbing system beneath Kilauea.

Historical records since 1 January 2000 document 24 such swarms in the vicinity. Annual counts include three in 2000, one in 2001, eight in 2003, five in 2004, one in 2005, two in 2006, and four in 2007. These episodes underscore the recurrent nature of seismic swarms driven by Hawaii's dynamic volcanic environment, where magma movement periodically triggers clusters of earthquakes.

Overall, VS20081205.1 exemplifies the persistent low-level seismic unrest characteristic of the Volcano region. Such swarms provide valuable data for monitoring volcanic hazards and refining models of subsurface processes.

References

• SeismoSight internal swarm classification records
• USGS Hawaiian Volcano Observatory volcanic seismicity reports