Seismic Swarm VS20030712.1: Analysis of Earthquake Activity Near Volcano, Hawaii
A seismic swarm designated VS20030712.1 occurred 4 km SSW of Volcano, Hawaii, from 05:50 on 12 July 2003 to 01:05 on 14 July 2003. Over 43 hours and 14 minutes, the event registered 34 earthquakes, providing a snapshot of subsurface activity in one of Earth’s most dynamic volcanic regions.
The Hawaiian Islands form through hotspot volcanism, where the Pacific Plate moves over a mantle plume. This process sustains the active volcanoes of the Big Island, including Kilauea, located immediately adjacent to the swarm epicenter. Kilauea’s summit and rift zones experience frequent seismicity driven by magma intrusion, flank movement, and associated faulting. Depths recorded during the swarm, ranging from 2 km to 13 km, align with typical source zones for volcanic earthquakes beneath the volcano’s edifice and south flank.
Magnitudes remained modest, between 1.1 and 2.2, consistent with the background seismicity that characterizes Kilauea’s restless periods. The temporal distribution showed peak activity on 12 July, with 29 events, followed by a sharp decline to four events on 13 July and a single closing event early on 14 July. Depths clustered between 6 km and 12 km for most events, suggesting a mid-crustal source possibly linked to magma transport or pressurization beneath the southwest rift zone.
Historical context indicates that such swarms are recurrent. Since 1 January 2000, five swarms have been documented in the immediate area: three in 2000, one in 2001, and the present swarm in 2003. These episodes reflect the persistent volcanic and tectonic stresses that define the region’s geology.
The 2003 swarm did not culminate in an eruption, illustrating that not all seismic clusters at Kilauea lead to surface activity. Instead, they often represent adjustments within the volcanic system. Continued monitoring by the U.S. Geological Survey’s Hawaiian Volcano Observatory remains essential for interpreting these patterns and assessing hazards.
- U.S. Geological Survey, Hawaiian Volcano Observatory reports on Kilauea seismicity (2000–2003)
- SeismoSight internal swarm classification database, event VS20030712.1