Seismic Swarm VS20230822.1 Near Volcano, Hawaii: Characteristics and Regional Context

Seismic swarm VS20230822.1 was recorded 8 km southwest of Volcano, Hawaii, beginning at 04:38 on 21 August 2023 and concluding at 01:59 on 12 September 2023. Over 525 hours and 21 minutes, the swarm comprised 552 earthquakes. This event aligns with patterns of episodic seismic activity driven by magmatic and tectonic processes on the Island of Hawaii.

The Island of Hawaii sits above the Hawaiian hotspot, where the Pacific Plate moves northwest over a mantle plume. This setting produces the active shield volcanoes Kilauea and Mauna Loa. Kilauea, located within Hawaii Volcanoes National Park, exhibits persistent background seismicity linked to magma transport through rift zones and summit reservoirs. Earthquakes in this region typically occur at shallow depths (0–5 km) and reflect brittle failure of rock in response to dike intrusions or pressure changes within the volcanic system.

Analysis of the first 100 events in swarm VS20230822.1 shows predominantly low-magnitude earthquakes, with the largest reaching 2.4. Depths ranged from 0 to 3 km, and the majority clustered between 0 and 2 km. Early activity featured several events above magnitude 2.0 within the first 48 hours, followed by a high rate of smaller events (magnitudes 0.1–1.0). This distribution is consistent with fluid-induced fracturing or magma migration at shallow levels beneath the southwest flank of Kilauea.

Historical records indicate 95 seismic swarms in the same area since 1 January 2000. Annual counts vary, with notable peaks in 2020 (14 swarms), 2018 (9), 2021 (9), and 2023 (9). Earlier years such as 2003 (8) and 2004 (5) also recorded elevated activity. These swarms commonly occur along Kilauea’s East and Southwest Rift Zones and are often associated with inflation or deflation cycles at the summit.

Seismic swarms in this volcanic environment serve as indicators of subsurface unrest but do not always culminate in eruptive activity. Continuous monitoring by the U.S. Geological Survey Hawaiian Volcano Observatory integrates seismic, deformation, and gas data to assess hazard levels. Swarm VS20230822.1 remained within typical background thresholds for the region and did not trigger elevated alert levels.

References

U.S. Geological Survey Hawaiian Volcano Observatory – Kilauea activity summaries (ongoing monitoring data through 2023).
Hawaii Volcanoes National Park geologic resources – volcanic history and structure descriptions.