Seismic Swarm S20121025.1: Analysis of Earthquake Activity on the Island of Hawaii

Seismic swarm S20121025.1 occurred on the Island of Hawaii from 04:47 on 24 October 2012 to 06:42 on 3 November 2012. Over 241 hours and 54 minutes, the swarm registered 134 earthquakes. Analysis of the first 100 events reveals predominantly low-magnitude activity concentrated at shallow depths. Magnitudes ranged from 0.3 to 2.8, with the majority falling between 1.0 and 2.5. Depths were mostly 0–3 km, though several events reached 28 km and one reached 40 km, indicating varied focal zones within the volcanic system. The sequence began with events at 2.0 and 1.1 magnitude shortly after initiation, followed by clusters of activity on 24–26 October featuring peaks at 2.8 magnitude. Subsequent days showed sustained low-level seismicity, with notable events on 29–31 October including multiple 2.5–2.7 magnitude quakes. Depths remained shallow for most recorded events, consistent with near-surface processes, while deeper outliers suggest possible connections to broader crustal structures. The Island of Hawaii lies within an active volcanic province shaped by the Hawaiian hotspot. This mantle plume has driven the formation of the Hawaiian-Emperor seamount chain over millions of years, with the island representing the youngest and most volcanically active segment. Primary volcanoes include Kilauea, Mauna Loa, and Mauna Kea, where magma movement frequently triggers earthquake swarms through dike intrusions and pressure changes in the crust. Earthquake swarms in this region have been documented since at least 2000, with 31 recorded up to 2012. Annual counts varied, including eight swarms in 2003 and four each in 2004, 2007, 2011, and 2012. Such swarms often precede or accompany eruptive episodes, reflecting the dynamic interplay between tectonics and volcanism in the hotspot setting.

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USGS Hawaiian Volcano Observatory reports on regional geology and seismicity.