Seismic Swarm VS20230520.1 Near Volcano, Hawaii: Characteristics and Regional Context

A seismic swarm designated VS20230520.1 occurred 8 km west of Volcano, Hawaii, from 01:09 on 20 May 2023 to 20:06 on 26 May 2023. Over 162 hours and 57 minutes, 135 earthquakes were recorded. Analysis of the first 100 events reveals predominantly shallow activity, with depths ranging from 0 km to 5 km and magnitudes between 0.4 and 3.6. The sequence began with low-magnitude events clustered around 1–2, followed by a notable increase in both frequency and intensity on the evening of 20 May, including peaks of 3.0 and 3.6. Subsequent days showed continued moderate activity, with many events between 1.5 and 2.5, interspersed with smaller tremors.

This pattern aligns with typical swarm behavior in volcanic regions, where events occur in rapid succession without a single dominant mainshock. Depths remained consistently shallow, suggesting involvement of near-surface crustal processes. The provided event catalog indicates no clear migration of hypocenters, consistent with localized stress adjustments.

The Island of Hawaii lies above the Hawaiian hotspot, where the Pacific Plate moves over a mantle plume, fueling ongoing volcanism. The swarm location is situated near Kilauea volcano, one of the world's most active. Kilauea's east rift zone and summit caldera have produced frequent eruptions and associated seismicity for centuries. Earthquake swarms in this area commonly result from magma intrusion, dike propagation, or fault slip induced by volcanic loading.

Historical records document 87 swarms in the region since 2000, with notable yearly totals including 13 in 2020, 9 in 2018, and 8 in both 2003 and 2021. These episodes reflect the persistent tectonic and magmatic dynamics of the hotspot setting. The 2018 eruption of Kilauea, which involved extensive lava flows and caldera collapse, was preceded and accompanied by intense seismic swarms, underscoring the link between such sequences and volcanic unrest.

No significant surface deformation or eruptive activity was associated with VS20230520.1, indicating it likely represented a minor adjustment within the volcanic system rather than a precursor to renewed eruption. Continued monitoring by the Hawaiian Volcano Observatory remains essential for interpreting future swarms in this geologically active environment.

References

USGS Hawaiian Volcano Observatory reports on Kilauea seismicity.
Hawaii Volcanoes National Park geological summaries.
Peer-reviewed studies on Hawaiian hotspot tectonics (e.g., Journal of Volcanology and Geothermal Research).