Seismic Swarm VS20230105.1 Near Volcano, Hawaii: Geological Context and Event Analysis

A seismic swarm designated VS20230105.1 was recorded 5 km southwest of Volcano, Hawaii, from 01:48 on 5 January 2023 to 06:21 on 7 January 2023. Over 52 hours and 32 minutes, the sequence included 67 earthquakes, with the majority occurring at shallow depths of 0–4 km. Magnitudes ranged from 0.2 to 3.2, consistent with typical volcanic swarm behavior driven by fluid migration or minor magma movement beneath the active volcanic edifice. The region lies on the Big Island of Hawaii, part of the Hawaiian-Emperor seamount chain formed by the Hawaiian hotspot. Volcano sits adjacent to Kīlauea, one of the world’s most active shield volcanoes, where persistent summit and rift-zone activity has shaped the landscape for centuries. Kīlauea’s magma system frequently produces earthquake swarms as pressure changes within shallow reservoirs and dikes. Historical records document repeated swarms linked to eruptions in 1924, 1959–1960, 1974, 1983–2018, and the dramatic 2018 lower East Rift Zone event that destroyed hundreds of structures. Since 1 January 2000, 78 swarms have been identified in the immediate area. Annual counts show variability: three in 2000, one in 2001, eight in 2003, five in 2004, one in 2005, two in 2006, four in 2007, one in 2008, three in 2011, four in 2012, one in 2013, two in 2014, three in 2015, two in 2016, two in 2017, nine in 2018, three in 2019, eleven in 2020, seven in 2021, and six in 2022. This pattern reflects ongoing volcanic unrest punctuated by episodic magma intrusions. Within VS20230105.1, the largest event reached magnitude 3.2 at 01:28 on 6 January at 0 km depth. Multiple events of magnitude 2.0–2.8 clustered between 01:00 and 04:00 that day, all at depths of 0–3 km. Later activity included a single deeper event of magnitude 1.7 at 23 km on 7 January, possibly representing a separate stress adjustment. The predominance of events at or above 1 km depth indicates shallow crustal processes rather than deeper tectonic sources. Such swarms are common precursors or companions to volcanic unrest in Hawaii. They rarely produce damaging ground shaking but serve as valuable indicators for monitoring networks operated by the U.S. Geological Survey Hawaiian Volcano Observatory. Continued seismic surveillance remains essential given Kīlauea’s history of sudden eruptive resumption. References
U.S. Geological Survey Hawaiian Volcano Observatory earthquake catalog (2000–2023).
SeismoSight internal swarm classification database.