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Location:
40 km ESE of Naalehu, Hawaii
Period:
10 Sep 2001 23:52:27 - 14 Sep 2001 13:06:47 (3 days 13 hours 14 minutes)
Volcanoes in 100km radius:
Kama'ehuakanaloa(8km), Kilauea(62km), Mauna Loa(79km)
Earthquakes:
50
6 swarms found nearby.
2005
7 Dec
3 days 11 hours
117 earthquakes
2017
29 Jun
2 days 9 hours
51 earthquakes
2020
11 May
3 days 16 hours
131 earthquakes
2021
S20210205.1(21.6km)
4 Feb
25 days 20 hours
475 earthquakes
15 Dec
2 days 7 hours
38 earthquakes
2024
2 Nov
2 days 11 hours
59 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20010911.1 Near Naalehu, Hawaii: Geological Context and Event Analysis

Seismic swarm S20010911.1 occurred approximately 40 km east-southeast of Naalehu on the island of Hawaii. The sequence began at 23:52 on 10 September 2001 and concluded at 13:06 on 14 September 2001, spanning 85 hours and 14 minutes. During this period, 50 earthquakes were recorded, with the majority occurring at depths between 7 km and 19 km. Magnitudes ranged from 1.5 to 4.9, reflecting typical swarm characteristics driven by fluid migration or stress adjustments within the volcanic edifice rather than a single large rupture.

The region lies on the southern flank of Hawaii Island, where the Pacific Plate interacts with the Hawaiian hotspot. This area experiences frequent seismic activity due to volcanic processes, including magma intrusion and gravitational spreading of the volcanic slopes. Historical records document numerous swarms associated with Kilauea and Mauna Loa volcanoes, often preceding or accompanying eruptive episodes. The 2001 swarm aligns with patterns observed in the south flank, where earthquakes commonly occur along fault systems accommodating seaward movement of the volcanic mass.

Key events within the swarm included a magnitude 4.7 earthquake at 00:09 on 11 September at 12 km depth, followed by a magnitude 4.9 event at 13:11 on 13 September at 11 km depth. These larger shocks were interspersed with numerous smaller events clustered around 10–12 km depth, indicating a concentrated source zone. Depths remained relatively consistent, suggesting activity within the brittle upper crust overlying the hotspot plume.

Hawaii’s geology is dominated by shield volcanoes built over millions of years. The island’s southern region features young lava flows and active faulting linked to the ongoing growth of the volcanic pile. Updated monitoring by the U.S. Geological Survey confirms that such swarms are integral to the island’s dynamic landscape, with similar sequences recorded in subsequent decades. The 2001 activity did not culminate in surface rupture or eruption, consistent with many non-eruptive swarms in the area.

The swarm’s temporal distribution showed peak activity within the first 24 hours, tapering thereafter. This pattern is characteristic of volcanic swarms, where initial stress release triggers aftershocks and secondary events. Depths averaging near 11 km correspond to the transition zone between the volcanic pile and underlying oceanic crust, a common locus for Hawaiian seismicity.

References

  • U.S. Geological Survey, Hawaiian Volcano Observatory reports on regional seismicity.
  • SeismoSight internal classification data for swarm S20010911.1.