Seismic Swarm VS20180411.1: Analysis of Activity Near Volcano, Hawaii

The seismic swarm designated VS20180411.1 occurred 5 km southwest of Volcano, Hawaii, on the Big Island. It began at 17:08 on 10 April 2018 and concluded at 04:37 on 13 April 2018, spanning 59 hours and 29 minutes. During this interval, 153 earthquakes were recorded. Analysis of the first 100 events reveals predominantly low-magnitude activity clustered at shallow depths, consistent with magma-driven processes in an active volcanic setting. Magnitudes ranged from 0.4 to 2.9, with the majority falling between 1.7 and 2.5. Depths were mostly between 1 km and 12 km, although a few events reached 30 km. The initial event on 10 April registered magnitude 2.2 at 6 km depth. Subsequent activity on 11 April included several magnitude 2.4–2.9 shocks at depths of 6–10 km, indicating possible fluid migration or pressure changes within the volcanic system. Paired events with identical timestamps but differing magnitudes suggest simultaneous rupture on adjacent faults or multiplet sequences. By 12 April, the swarm maintained a steady rate with events concentrated at 3–10 km depth. Notable clusters occurred around 00:30, 02:40, and 06:02, each featuring paired magnitudes near 2.5. The data show no clear escalation toward larger events within the first 100 recordings, pointing to a diffuse, non-destructive swarm typical of volcanic unrest rather than tectonic mainshock-aftershock sequences. This region lies within the Kilauea volcanic edifice, part of the Hawaiian hotspot chain formed by the Pacific plate moving over a mantle plume. Kilauea is a basaltic shield volcano characterized by frequent effusive eruptions and persistent summit caldera activity. Its geology features rift zones, flank faults, and shallow magma reservoirs that periodically trigger earthquake swarms through dike intrusion and hydrothermal fluid movement. Historical records document repeated swarms in this area since at least 2000, with annual counts varying from one to eight episodes per year. The 2018 swarm preceded the major lower East Rift Zone eruption that began in early May, underscoring the value of swarm monitoring for eruption forecasting. Depths predominantly under 10 km align with the known location of Kilauea’s shallow magma storage and transport pathways. Such activity reflects the dynamic interplay between magma supply from depth and the volcano’s south-flank instability driven by gravitational spreading. In summary, swarm VS20180411.1 exemplifies the recurrent seismic signatures of Kilauea’s magmatic system. Continued surveillance of similar patterns remains essential for assessing volcanic hazards in this geologically active locale.

References

USGS Hawaiian Volcano Observatory reports on Kilauea seismicity and 2018 eruption chronology.
Hawaii Volcanoes National Park geological summaries on shield volcano structure and rift zones.