Seismic Swarm VS20220921.1: Analysis of Activity Near Volcano, Hawaii

A notable seismic swarm designated VS20220921.1 was recorded 6 km southwest of Volcano, Hawaii, beginning at 13:59 on 20 September 2022 and concluding at 15:25 on 21 September 2022. Over this 25-hour period, 100 earthquakes were detected, providing valuable data on subsurface dynamics in one of Earth’s most active volcanic regions.

The events clustered predominantly at shallow depths, with the majority occurring at 0–3 km. Magnitudes ranged from 0.3 to 2.9, with the largest event reaching 2.9 at 03:32 on 21 September. Multiple earthquakes often occurred within seconds of one another, reflecting rapid stress release along fractures. The temporal distribution showed peak activity between 01:00 and 06:00 on 21 September, followed by a gradual decline toward the swarm’s termination.

This swarm occurred within the volcanic framework of Hawai‘i Island, where the Hawaiian hotspot fuels ongoing magma ascent beneath Kīlauea and Mauna Loa. The town of Volcano lies adjacent to Hawai‘i Volcanoes National Park, an area shaped by repeated effusive and explosive eruptions over millennia. Shallow seismicity commonly signals magma migration or pressurization of the volcanic edifice, consistent with the region’s documented behavior.

Historical records indicate persistent swarm activity in the area. Since 1 January 2000, 78 swarms have been identified, with annual counts varying significantly: 13 in 2020, 9 in 2018, and 8 in 2003. Earlier years such as 2001 and 2005 recorded only single swarms, underscoring the episodic nature of these sequences. These events frequently correlate with cycles of magma replenishment and withdrawal beneath the summit and rift zones.

The 2022 swarm aligns with patterns observed in prior episodes, where low-magnitude, high-frequency events occur without immediate surface rupture. Such activity contributes to monitoring efforts aimed at forecasting volcanic unrest. Continued instrumentation by seismic networks enables precise tracking of hypocenters and focal mechanisms, refining models of crustal deformation.

In summary, VS20220921.1 exemplifies the routine yet informative seismicity that characterizes Hawai‘i’s volcanic landscape. Integration of swarm statistics with long-term geological records supports improved hazard assessment for communities surrounding active vents.

References: USGS Hawaiian Volcano Observatory reports on Kīlauea seismicity Hawai‘i Volcanoes National Park geological summaries Global Volcanism Program database entries for Hawaiian volcanoes