Seismic Analysis of Swarm VS20180602.1 Near Volcano, Hawaii

The VS20180602.1 earthquake swarm was recorded 6 km southwest of Volcano, Hawaii, on the Island of Hawaiʻi. Activity began at 03:32 on 2 June 2018 and concluded at 15:43 on 9 June 2018, encompassing 119 events over 180 hours and 10 minutes. This swarm occurred within the seismically active East Rift Zone of Kīlauea volcano, where magma movement and crustal stress adjustments frequently generate earthquake sequences.

Examination of the first 100 events reveals predominantly shallow focal depths between 0 and 10 km, consistent with volcanic-tectonic processes near the surface. Magnitudes ranged from 0.7 to 3.1, with the largest event (M3.1) occurring on 3 June at 6 km depth. Many events appear in near-simultaneous pairs of lower- and higher-magnitude shocks, suggesting triggered slip along small faults or fluid migration. Early activity on 2 June featured numerous events at or near 0 km depth with magnitudes of 1.0–2.5, transitioning to slightly deeper events (4–9 km) by 4–8 June as the sequence evolved. This temporal deepening may reflect progressive stress transfer within the volcanic edifice.

Kīlauea is one of the world’s most active shield volcanoes, built by successive lava flows from a summit caldera and rift zones. The Island of Hawaiʻi comprises five major volcanoes, with Kīlauea and Mauna Loa remaining in their shield-building stage. Frequent earthquake swarms in this region arise from dike intrusions, flank movement along décollement faults, and hydrothermal fluid circulation. The 2018 swarm coincided with heightened eruptive activity at Kīlauea, underscoring the interplay between seismicity and magmatic processes.

Historical records since 1 January 2000 document 14 earthquake swarms in the same locale. These occurred in 2001 (1 swarm), 2003 (2), 2004 (1), 2006 (1), 2007 (3), 2011 (2), 2012 (1), and 2018 (3). The clustering in 2007 and 2018 highlights episodic periods of elevated volcanic unrest driven by magma supply variations from the Hawaiian hotspot.

Such swarms provide critical data for monitoring volcanic hazards. Shallow, low-magnitude sequences like VS20180602.1 typically indicate minor adjustments rather than imminent large eruptions, yet they warrant continued observation given Kīlauea’s dynamic setting.

References
USGS Earthquake Catalog
Hawaiian Volcano Observatory reports
SeismoSight internal swarm classification VS20180602.1