Seismic Swarm S20110302.1: Analysis of Activity Near Kilauea Volcano, Hawaii

Seismic swarm S20110302.1 occurred 6 km south of Volcano, Hawaii, on the Big Island. The sequence began at 04:38 on 1 March 2011 and concluded at 13:51 on 8 March 2011, spanning 177 hours and 13 minutes. During this period, 325 earthquakes were recorded. The swarm took place in a region dominated by Kilauea volcano, one of the world's most active shield volcanoes.

Kilauea forms part of the Hawaiian hotspot chain and lies within Hawaii Volcanoes National Park. Its geology features frequent magma intrusions, rift zone extensions, and caldera subsidence, all of which generate shallow seismicity. Earthquakes in this area typically occur at depths of 0–10 km and reflect brittle failure in the volcanic edifice or surrounding crust. Historical monitoring by the USGS Hawaiian Volcano Observatory shows that such swarms often precede or accompany eruptive episodes, as magma movement stresses surrounding rock.

The first 100 events of the swarm exhibited predominantly low magnitudes, with the majority between 0.2 and 2.8. The largest event reached magnitude 2.8 on 1 March at 21:24:25. Depths remained shallow, ranging from 0 to 9 km, consistent with volcanic rather than tectonic origins. Activity clustered in the initial 48 hours, with multiple events per hour during peak periods on 1–3 March. Magnitudes showed no clear escalation trend, suggesting a diffuse release of stress rather than a single mainshock-aftershock sequence.

Regional swarm history since 2000 indicates recurrent seismic episodes driven by Kilauea’s persistent activity. Twenty-seven swarms occurred between 2000 and 2011, with notable concentrations in 2003 (8 events) and 2004 (5 events). Earlier years recorded fewer episodes, reflecting variable magma supply rates. These patterns align with Kilauea’s long-term behavior, including the ongoing east rift zone eruptions that characterized the early 2010s.

The 2011 swarm contributed to broader monitoring efforts around Kilauea’s summit and upper east rift zone. Shallow depths and low magnitudes point to localized stress changes possibly linked to magma migration or gas release beneath the surface. No surface deformation or eruptive activity was directly tied to this specific sequence in available records, underscoring the value of dense seismic networks for distinguishing background volcanic noise from precursors.

Continued observation of similar swarms aids hazard assessment in this densely monitored volcanic setting. The data from S20110302.1 reinforce the importance of real-time analysis for understanding Kilauea’s dynamic subsurface processes.

References

• SeismoSight internal swarm classification records for S20110302.1 event parameters and historical swarm counts.
• USGS Hawaiian Volcano Observatory geological summaries on Kilauea structure and seismicity patterns (updated through 2023 monitoring archives).