Seismic Swarm VS20191001.1: Analysis of Activity Near Volcano, Hawaii

Seismic swarm VS20191001.1 occurred 8 km SSW of Volcano, Hawaii, registering 35 earthquakes over 56 hours and 56 minutes. The sequence began at 23:37 on 30 September 2019 and concluded at 08:33 on 3 October 2019. Events ranged in magnitude from 0.5 to 2.6, with depths mostly between 0 and 12 km, though one reached 28 km.

This swarm reflects typical volcanic seismicity in the region. Hawaii lies above a mantle hotspot that has generated the Hawaiian-Emperor seamount chain over millions of years. The Island of Hawaii hosts active shield volcanoes including Kilauea and Mauna Loa, where magma movement and crustal adjustments frequently trigger earthquake swarms. Swarms differ from mainshock-aftershock sequences by lacking a dominant event and instead showing clustered activity driven by fluid migration or dike intrusion.

Event timing showed an initial cluster on 1 October with multiple magnitude 0.7–1.7 quakes at shallow depths. Activity continued at a steady but lower rate through 2 October before a notable magnitude 2.6 event at 6 km depth on 3 October marked the sequence peak. Depths concentrated in the upper 12 km indicate brittle failure within the volcanic edifice and surrounding crust, consistent with Kilauea’s south flank dynamics.

Historical records since 2000 document 53 swarms in the area, with notable concentrations in 2003 (8 swarms), 2018 (9 swarms), and earlier years such as 2004 and 2007. These episodes align with known eruptive periods at Kilauea, including the 2018 lower East Rift Zone activity that produced widespread ground deformation and lava flows. Swarm frequency underscores the persistent volcanic-tectonic interaction in this hotspot setting.

The 2019 swarm remained modest in energy release and did not precede any immediate surface eruption. Such events nonetheless provide valuable data for monitoring magma pathways beneath the summit and rift zones. Continuous seismic networks operated by the U.S. Geological Survey help distinguish swarms from tectonic earthquakes and support hazard assessment for nearby communities.

References

USGS Hawaiian Volcano Observatory earthquake catalog and swarm reports.
Hawaii Volcanoes National Park geological summaries.
Scientific literature on Hawaiian hotspot volcanism and seismicity (e.g., publications in Journal of Volcanology and Geothermal Research).