Seismic Swarm S20260524.2: Analysis of Activity Near Honaunau-Napoopoo, Hawaii

Seismic swarm S20260524.2 occurred 12 km south-southeast of Honaunau-Napoopoo on the Island of Hawaii. The sequence began at 07:46 on 23 May 2026 and concluded at 16:07 on 24 May 2026, spanning 32 hours and 21 minutes. During this period, 26 earthquakes were recorded, with magnitudes ranging from 1.5 to 5.9 and depths primarily between 4 km and 26 km.

The swarm initiated with a magnitude 5.9 event at 22 km depth. Subsequent activity included multiple events above magnitude 3.0, such as a 3.9 quake at 23 km depth and two magnitude 3.2 events at depths of 21 km and 19 km. Shallower activity was limited, with one event at 4 km depth. Most events clustered between 16 km and 24 km, consistent with mid-crustal stress release in this volcanic region.

Honaunau-Napoopoo lies on the southwestern flank of Mauna Loa volcano within the active Hawaiian hotspot system. The geology features young basaltic lava flows overlying older shield volcano structures. Seismic activity in this area commonly arises from magma migration, volcanic inflation, or reactivation of faults associated with the volcanic edifice and the nearby Hilina fault system. Depths recorded in the swarm align with typical mid-crustal processes beneath the Kona coast, where the lithosphere experiences both volcanic and tectonic influences.

Since 2000, seven prior swarms have been documented in the vicinity. These occurred in 2015 (one swarm), 2016 (one), 2017 (two), 2020 (one), 2021 (one), and 2022 (one). Such recurrent swarms reflect the ongoing dynamic nature of Hawaii's volcanic environment, where episodic seismic clusters often precede or accompany volcanic unrest without leading to immediate eruptions.

This latest sequence highlights the persistent seismicity along the Kona coast. Monitoring by the Hawaiian Volcano Observatory continues to track these patterns, providing data essential for assessing volcanic hazards in one of the most active volcanic regions on Earth.

References

• United States Geological Survey, Hawaiian Volcano Observatory reports on Mauna Loa and Kona coast seismicity
• SeismoSight internal swarm classification database