Seismic Insights into Earthquake Swarm VS20060312.1 Near Volcano, Hawaii

The earthquake swarm VS20060312.1 occurred 8 km southwest of Volcano, Hawaii, a region shaped by the Hawaiian hotspot and frequent volcanic unrest. The swarm began at 06:21 on 11 March 2006 and ended at 11:34 on 14 March 2006, lasting 77 hours and 13 minutes while producing 41 earthquakes.

Magnitudes ranged from 0.8 to 2.5, with the majority falling between 1.0 and 1.9. Depths remained shallow, from 0 to 9 km, consistent with crustal adjustments above shallow magmatic sources. Activity clustered on 11 March, featuring the largest event of magnitude 2.5 at 19:39 and several magnitude 1.8–2.1 shocks within minutes. Subsequent days showed lower rates, with isolated events up to magnitude 2.3 on 12 March and magnitude 2.0 on 13 March. The final recorded quake reached magnitude 1.3 at 9 km depth on 14 March.

Such swarms reflect episodic stress release tied to magma migration or hydrothermal fluid movement beneath Kilauea’s flanks. Shallow focal depths indicate sources within the volcanic edifice rather than deeper tectonic faults. The tight temporal clustering and modest magnitudes typify non-eruptive swarms that relieve strain without immediate surface rupture.

Since 1 January 2000 the same area has hosted 21 swarms. Yearly counts peaked in 2003 (7 swarms) and 2004 (8 swarms), while 2001, 2005, and 2006 each recorded only one. This pattern underscores recurring volcanic-seismic cycles driven by the ongoing supply of magma from the hotspot.

Hawaii’s geology arises from the Pacific plate moving over a mantle plume, building shield volcanoes such as Kilauea. Continuous summit and rift-zone inflation produces precisely the shallow earthquake sequences observed in VS20060312.1. Long-term monitoring shows these swarms often precede or accompany changes in eruptive behavior, although this particular swarm remained aseismic at the surface.

References
SeismoSight internal swarm classification VS20060312.1
USGS Hawaiian Volcano Observatory volcanic and seismic background reports