Seismic Swarm VS20180423.1: Analysis of Activity Near Kilauea, Hawaii

Seismic swarm VS20180423.1 was recorded 5 km southwest of Volcano, Hawaii, beginning at 03:58 on 22 April 2018 and concluding at 23:40 on 29 April 2018. Over 187 hours and 42 minutes, the swarm produced 134 earthquakes. This event occurred within the seismically active Kilauea volcanic system on the Big Island, where tectonic and magmatic processes drive frequent ground movement.

The first 100 events revealed predominantly low-magnitude earthquakes, with values ranging from 0.5 to 2.9. Depths clustered near the surface, most between 0 and 3 km, though isolated events reached 13 km, 25 km, and 28 km. Early activity on 22 April included a 2.8 magnitude quake at 1 km depth, followed by several events exceeding magnitude 2.5 within the first 24 hours. Subsequent days showed sustained shallow seismicity, with repeated clusters around 1–2 km depth and occasional deeper signals. This pattern indicates shallow crustal fracturing likely linked to fluid or magma migration beneath the volcano's flank.

Kilauea is a classic shield volcano built by fluid basaltic lava flows, situated above the Hawaiian hotspot. Its geology features rift zones, caldera structures, and pervasive faulting that facilitate both eruptive and intrusive activity. Seismic swarms in this setting commonly precede or accompany magma movement, reflecting stress changes in the volcanic edifice.

Historical records since 2000 document 45 swarms in the immediate region. Yearly tallies include three in 2000, one in 2001, eight in 2003, four in 2004, one in 2005, two in 2006, four in 2007, one in 2008, four each in 2011 and 2012, one in 2013, two in 2014, three in 2015, two each in 2016 and 2017, and three in 2018. These episodes underscore the persistent unrest that defines Kilauea's dynamic environment.

The April 2018 swarm fits within this established framework of episodic seismic bursts. Its concentration of shallow, moderate-magnitude events aligns with typical precursory signals observed in the volcano's recent history.

References

USGS Hawaiian Volcano Observatory reports on Kilauea seismicity
Hawaii Volcanoes National Park geological summaries
Smithsonian Institution Global Volcanism Program database