Seismic Swarm VS20201023.1: Analysis of Activity Near Kilauea Volcano, Hawaii
An earthquake swarm designated VS20201023.1 was recorded 9 km west-southwest of Volcano, Hawaii, on the Big Island. The sequence began at 13:39 on 22 October 2020 and concluded at 07:59 on 30 October 2020, spanning 186 hours and 19 minutes. A total of 177 earthquakes were detected during this period. The swarm occurred in a region dominated by Kilauea volcano, one of the world's most active shield volcanoes, where persistent magma movement through rift zones routinely generates seismic swarms.
Kilauea lies within Hawaii Volcanoes National Park and forms part of the Hawaiian hotspot chain. Its summit caldera and East Rift Zone are primary loci for both eruptive and intrusive activity. Seismic swarms in this setting typically reflect dike propagation or pressure changes in the shallow magmatic system rather than tectonic faulting. Depths recorded in the present swarm ranged from 0 km to 10 km, consistent with the shallow crustal environment beneath the volcano's flanks.
Analysis of the first 100 events reveals a predominance of low-magnitude earthquakes. Magnitudes clustered between 0.6 and 3.0, with the majority falling in the 1.7–2.4 range. The largest event reached magnitude 3.0 at 11:43:42 on 23 October at a depth of 3 km. Shallow events (0–3 km) accounted for the bulk of detections, indicating activity concentrated in the upper volcanic edifice. A secondary cluster of slightly deeper events (4–10 km) appeared on 24 October, possibly marking minor adjustments deeper in the conduit system. Temporal distribution showed peak rates during the afternoon and evening of 23 October, followed by a gradual decline.
The swarm fits established patterns of volcanic seismicity at Kilauea. Since 1 January 2000, 63 swarms have been documented in the same locale. Yearly counts include three in 2000, one in 2001, eight in 2003, five in 2004, one in 2005, two in 2006, four in 2007, one in 2008, four 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, and eight in 2020. These episodes commonly precede or accompany surface deformation and, in some cases, eruptive outbreaks along the East Rift Zone.
No significant surface deformation or eruptive activity was associated with VS20201023.1, suggesting an intrusive rather than extrusive episode. Such non-eruptive swarms contribute to long-term monitoring data used by the Hawaiian Volcano Observatory to assess magma supply rates and forecast potential unrest.
References
- Hawaiian Volcano Observatory, U.S. Geological Survey – Kilauea monitoring summaries (2020–2023 updates)
- SeismoSight internal swarm classification database – VS20201023.1 parameters and historical swarm catalog since 2000