Seismic Swarm VS20201118.1: Analysis of Activity Near Volcano, Hawaii

A notable seismic swarm, designated VS20201118.1, occurred 5.7 km northeast of Volcano, Hawaii, on the Big Island. The sequence began at 01:33 on 18 November 2020 and concluded at 09:55 on 19 November 2020, spanning 32 hours and 21 minutes. During this period, 43 earthquakes were recorded, with magnitudes ranging from 0.4 to 2.5 and depths primarily between 0 and 6 km.

The events clustered in two main phases, with heightened activity during the afternoon of 18 November. Multiple events reached magnitude 2.0 or above, including peaks of 2.5 at shallow depths. These characteristics align with typical patterns observed in volcanic regions, where swarms often reflect fluid migration or stress adjustments within the crust rather than a single large rupture.

Hawaii’s geology is dominated by hotspot volcanism, with Kilauea volcano serving as a primary focus of activity. The region experiences frequent seismic swarms due to magma movement beneath the surface, interactions along rift zones, and gravitational adjustments on the volcanic edifice. Historical records since 2000 indicate 62 such swarms in the area, distributed across multiple years with notable concentrations in 2003 (8 swarms), 2018 (9 swarms), and 2020 (8 swarms). Earlier periods such as 2000 and 2007 each recorded 3–4 events, underscoring the persistent nature of this seismicity.

Kilauea’s summit and upper East Rift Zone have long been sites of recurring earthquake clusters. These swarms contribute to monitoring efforts that track volcanic unrest, as they frequently precede or accompany changes in lava lake levels, ground deformation, or eruptive episodes. Depths in the reported swarm remained predominantly shallow, consistent with activity in the volcanic crust above the main magma reservoir.

The 2020 swarm fits within the broader context of Hawaii’s dynamic volcanic system, where seismic rates can fluctuate in response to both magmatic and tectonic processes. Long-term statistics reveal episodic increases, such as the elevated count in 2018 coinciding with a major eruptive period at Kilauea. Continued observation of such sequences supports improved forecasting of volcanic hazards in this high-activity zone.

References

• United States Geological Survey (USGS) Hawaiian Volcano Observatory reports on Kilauea seismicity.
• SeismoSight internal swarm classification database for event parameters and historical counts.