Seismic Swarm S20180505.2: Analysis of Activity Near Kilauea, Hawaii

Seismic swarm S20180505.2 was recorded 25 km south-southeast of Volcano, Hawaii, beginning at 13:27 on 4 May 2018 and concluding at 18:11 on 7 May 2018. In the span of 76 hours and 44 minutes, 153 earthquakes were detected. This event occurred within the tectonically active south flank of Kilauea volcano, a region shaped by the Hawaiian hotspot and characterized by frequent magma-driven seismicity.

The first 100 events reveal predominantly shallow focal depths, with the majority occurring between 0 and 10 km. Magnitudes remained modest, clustering between 1.0 and 3.0, though two events reached 4.6 and 4.9 on 4 May. Depth variations included occasional deeper readings up to 32 km, indicating possible involvement of both crustal and upper-mantle processes. Temporal distribution showed peak activity in the initial 24 hours, followed by a gradual decline, consistent with swarm behavior driven by fluid migration or stress adjustment along pre-existing faults.

Kilauea lies on the Big Island of Hawaii and ranks among Earth’s most active volcanoes. Its eruptions are fed by a persistent magma conduit rising from the Hawaiian hotspot, a mantle plume that has constructed the Hawaiian-Emperor seamount chain over tens of millions of years. The south flank experiences recurrent swarms due to seaward sliding of the volcanic edifice along a basal décollement, a process documented through geodetic and seismic monitoring.

Historical records maintained by SeismoSight indicate 47 swarms in the same locale since 1 January 2000. Yearly counts include three in 2000, one in 2001, seven in 2003, five in 2004, and additional clusters through 2018, underscoring the persistent nature of this seismic regime.

References

USGS Hawaiian Volcano Observatory reports on Kilauea structure and 2018 activity.
Hawaii Seismic Network catalog summaries for regional event statistics.
SeismoSight internal swarm classification database.