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Location:
20 km E of Honaunau-Napoopoo, Hawaii
Period:
4 Dec 2020 17:44:24 - 10 Dec 2020 07:35:13 (5 days 13 hours 50 minutes)
Volcanoes in 100km radius:
Mauna Loa(5km), Hualalai(30km), Kilauea(39km), Mauna Kea(41km), Kama'ehuakanaloa(76km)
Earthquakes:
110
20 swarms found nearby.
2004
28 Aug
24 days 12 hours
397 earthquakes
VS20041012.1(10.4km)
11 Oct
19 days 12 hours
360 earthquakes
VS20041110.1(16.1km)
9 Nov
24 days 3 hours
334 earthquakes
14 Dec
15 days 10 hours
342 earthquakes
2006
VS20060312.1(28.4km)
11 Mar
3 days 5 hours
41 earthquakes
2015
1 May
6 days 18 hours
118 earthquakes
23 Jul
23 hours
34 earthquakes
2016
3 Jul
6 days 16 hours
84 earthquakes
2017
7 Apr
4 days 14 hours
129 earthquakes
15 Apr
1 day 20 hours
56 earthquakes
2020
S20200302.1(23.2km)
1 Mar
4 days 18 hours
82 earthquakes
2021
28 Feb
4 days 16 hours
47 earthquakes
S20210318.1(26.1km)
18 Mar
2 days 15 hours
113 earthquakes
VS20210329.1(10.3km)
29 Mar
8 days 10 hours
279 earthquakes
7 Apr
12 days 0 hours
300 earthquakes
2022
3 Feb
5 days 5 hours
170 earthquakes
2 Aug
3 days 9 hours
131 earthquakes
23 Sep
14 days 19 hours
375 earthquakes
VS20221128.1(13.4km)
27 Nov
11 days 2 hours
416 earthquakes
2026
S20260524.2(29.2km)
23 May
1 day 8 hours
26 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20201205.1 Near Honaunau-Napoopoo, Hawaii

A seismic swarm designated S20201205.1 was recorded beginning at 17:44 on 4 December 2020 and concluding at 07:35 on 10 December 2020, approximately 20 km east of Honaunau-Napoopoo on the Island of Hawaii. Over 133 hours and 50 minutes, the sequence produced 110 earthquakes. Analysis of the first 100 events reveals predominantly shallow activity, with focal depths ranging from -3 km to 4 km and magnitudes between 0.6 and 4.0. The initial event reached magnitude 4.0 at 4 km depth, followed by numerous events clustered between 1.0 and 3.3 in magnitude during the first two days. Later stages showed a decline in larger events, with most registering below magnitude 2.0.

The region lies on the western flank of the Big Island, where the Hawaiian hotspot has built a volcanic edifice through successive shield volcanoes. Honaunau-Napoopoo sits within the South Kona district, influenced by the ongoing evolution of Mauna Loa and Kilauea. Seismicity here commonly arises from magma migration, crustal adjustment, and fault slip along the Hilina and Kealakekua fault systems. Depths recorded in the swarm align with typical upper-crustal volcanic processes in Hawaii, where events often occur within the first few kilometers beneath the surface.

Historical records indicate that seismic swarms are recurrent in this setting. Since 2000, eleven such swarms have been documented in the broader area, occurring in 2004 (four events), 2006 (one), 2015 (two), 2016 (one), 2017 (two), and 2020 (one). These episodes reflect the dynamic interplay between volcanic loading and tectonic stress release characteristic of the Hawaiian Islands.

Patterns within the December 2020 swarm include repeated low-magnitude aftershocks following the initial magnitude-4.0 event, with many events exhibiting negative depths suggestive of near-surface or slightly elevated sources relative to the reference datum. Activity intensified on 5 and 8 December, featuring several events above magnitude 2.5, before tapering. Such sequences contribute to ongoing monitoring of volcanic unrest and help refine models of crustal deformation in Hawaii's active volcanic zones.

References

USGS Earthquake Catalog
Hawaii Volcano Observatory reports
Hawaiian Volcano Observatory geological summaries