Seismic Swarm S20220528.1 Near Pāhala, Hawaii

Seismic swarm S20220528.1 was recorded 12 km east-southeast of Pāhala on Hawaii Island. The sequence began at 21:21 on 27 May 2022 and concluded at 21:54 on 3 June 2022, spanning 168 hours and 32 minutes. A total of 110 earthquakes were detected during this period.

The Pāhala area lies on the southern flank of Kīlauea volcano within the active volcanic zone of the Hawaiian hotspot. This geological setting produces frequent earthquake swarms driven by magma movement, dike intrusions, and associated stress changes in the crust. Earthquake depths in the swarm ranged primarily from 22 km to 41 km, consistent with activity occurring in the deeper portions of the volcanic system beneath the island's southeast flank.

Analysis of the first 100 events shows magnitudes between 1.5 and 3.6. The majority clustered between 1.7 and 2.3, with isolated larger events including a magnitude 2.9 on 28 May at 36 km depth and a magnitude 3.6 on 29 May at 28 km depth. Depths remained relatively stable around 30–35 km for most events, though a few shallower and deeper outliers appeared. Timing indicates peak activity during the first 48 hours, followed by a gradual decline.

Hawaii Island experiences recurrent seismic swarms linked to its active shield volcanoes. Since 1 January 2000, 47 swarms have been documented in the region. Yearly counts include one in 2000, three in 2003, two in 2004, one in 2005, three in 2007, one in 2008, one in 2011, one in 2013, one in 2014, four in 2015, two in 2016, six in 2018, three in 2019, nine in 2020, eight in 2021, and one in 2022 prior to the present sequence.

Such swarms contribute to monitoring volcanic unrest and flank stability. Continued observation supports assessment of potential eruptive or seismic hazards in this tectonically dynamic environment.

References
SeismoSight internal swarm classification records.
USGS Hawaiian Volcano Observatory geological summaries for the Pāhala–Kīlauea region.