Seismic Swarm S20231026.1: Analysis of Recent Activity on Hawaiʻi Island

Seismic swarm S20231026.1 occurred on the Island of Hawaii from 00:50 on 26 October 2023 to 09:29 on 28 October 2023. Over 56 hours and 38 minutes, 62 earthquakes were recorded. The events clustered in a region associated with the island's active volcanic systems, primarily involving shallow depths and low to moderate magnitudes.

The recorded earthquakes showed magnitudes ranging from 0.3 to 2.7, with the majority falling between 1.5 and 2.2. Depths were predominantly shallow, concentrated between 0 and 8 km, though one outlier reached 30 km. Activity peaked during the first day, with frequent events in the afternoon and evening of 26 October, followed by a gradual decline through 27 and 28 October. This temporal pattern aligns with typical swarm behavior driven by fluid migration or stress adjustments in volcanic crust.

Hawaiʻi Island's geology stems from its position over the Hawaiian hotspot, where upwelling mantle material fuels shield volcanoes including Kīlauea and Mauna Loa. These structures produce frequent seismicity through magma intrusion, caldera subsidence, and faulting along rift zones. Earthquake swarms here often precede or accompany eruptive episodes, reflecting pressure changes within the volcanic plumbing system. Historical records indicate persistent activity tied to these processes, with the island experiencing both volcanic and tectonic events.

Since 2000, 95 swarms have been documented on the island. Annual counts include 3 in 2000, 1 in 2001, 8 in 2003, 5 in 2004, 1 in 2005, 2 in 2006, 4 in 2007, 1 in 2008, 3 in 2011, 4 in 2012, 1 in 2013, 2 in 2014, 3 in 2015, 2 in 2016, 2 in 2017, 9 in 2018, 4 in 2019, 13 in 2020, 8 in 2021, 7 in 2022, and 12 in 2023. This distribution highlights recurring clusters, many linked to Kīlauea's East Rift Zone or summit activity.

Swarm S20231026.1 fits within this established framework. Its shallow focus and modest energy release suggest localized adjustments rather than a major tectonic shift. Such events contribute to ongoing monitoring efforts that track magma movement and inform hazard assessments for nearby communities.

References

USGS Hawaiian Volcano Observatory reports on regional seismicity.
Hawaiian Volcano Observatory historical earthquake catalogs.
Scientific literature on Hawaiian hotspot volcanism and swarm mechanics.