Seismic Swarm S20120605.1: Geological Context and Analysis Near Volcano, Hawaii

Seismic swarm S20120605.1 occurred 6 km south of Volcano, Hawaii, within the active Kilauea volcanic system. The sequence began at 21:21 on 4 June 2012 and concluded at 01:22 on 9 June 2012, registering 37 earthquakes over approximately 100 hours. This event aligns with patterns of volcanic seismicity driven by magma movement in the Hawaiian hotspot region.

The swarm featured predominantly shallow events, with depths clustered between 0 and 7 km for most earthquakes. Notable larger events included a magnitude 3.5 quake at 01:23 on 5 June at 0 km depth and a magnitude 3.6 event at 12:43 on the same day, also at 0 km depth. Other significant shocks reached magnitudes of 2.9, 2.7, 2.6, and 2.3, primarily at shallow depths. A few deeper events occurred, such as a magnitude 2.1 at 27 km on 7 June and one at 31 km on 9 June, suggesting possible interaction with deeper crustal structures. Magnitudes ranged from 0.5 to 3.6 overall, reflecting typical low-to-moderate energy release in volcanic swarms.

Geologically, the location lies on Hawaii's Big Island along the East Rift Zone of Kilauea, one of the world's most active volcanoes situated above a mantle hotspot. This setting produces frequent seismic swarms as magma ascends through fractures, causing rock fracturing and fluid migration. Historical volcanic activity in the area includes persistent lava flows and summit caldera dynamics, with seismicity serving as a key indicator of unrest. The 2012 swarm's shallow focus points to near-surface processes consistent with rift zone intrusions.

Since 2000, the region has experienced 30 documented swarms, underscoring recurrent volcanic-tectonic activity. Yearly distribution shows peaks in 2003 with eight swarms and 2004 with five, alongside smaller clusters in 2000, 2007, and 2011. The two swarms recorded in 2012, including this event, fit within the established pattern of episodic magma-driven seismicity.

Such swarms provide critical insights into subsurface dynamics, often preceding eruptive phases by highlighting fluid pathways. Monitoring these sequences aids in understanding long-term hotspot volcanism and associated hazards like ground deformation and gas emissions.

References

USGS Hawaiian Volcano Observatory seismic reports
Hawaii Volcanoes National Park geological surveys
Internal SeismoSight swarm classification database