129 km SSW of Adak, Alaska

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 30 km (19 mi) from the epicentre. Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

How big was it?

This earthquake released about 680 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 22,000× the energy of this one
2. Magna, Utah 2020 M 5.7 16,000× the energy of this one
3. Around the size people start to feel M 3.0 1.4× the energy of this one
4. This earthquake M 2.9 about 680 lb of TNT

Energy from the Gutenberg–Richter relation (log₁₀E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.

For this area

The largest earthquake within 50 km since 2016 was M 6.3 on 2024-12-09 — about 130,000 times the energy of this one.

Before 2016, the USGS record lists 62 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 111 km SW of Adak, Alaska · 46 km NNW of this epicentre Jan 4, 1912
2. 6.5 144 km SW of Adak, Alaska · 49 km WNW of this epicentre Apr 16, 1927
3. 6.3 134 km SW of Adak, Alaska · 42 km NW of this epicentre Aug 3, 1972
4. 6.2 101 km SW of Adak, Alaska · 40 km N of this epicentre Jun 2, 1940
5. 6.1 134 km SW of Adak, Alaska · 46 km NW of this epicentre Sep 30, 1992

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 50.9004, -177.6412. Map © OpenStreetMap contributors.

Aftershocks so far

45 earthquakes have been recorded within 50 km since this one.

1. 2.0 124 km SSW of Adak, Alaska 21:37 UTC
2. 2.9 116 km SW of Adak, Alaska 20:17 UTC
3. 2.5 145 km SSW of Adak, Alaska 10:45 UTC
4. 1.5 91 km SW of Adak, Alaska 15:26 UTC
5. 1.7 93 km SW of Adak, Alaska 09:41 UTC
6. 4.5 163 km SSW of Adak, Alaska 22:48 UTC
7. 2.7 107 km SW of Adak, Alaska 20:59 UTC
8. 1.9 108 km SW of Adak, Alaska 17:27 UTC
9. 3.1 124 km SSW of Adak, Alaska 01:43 UTC
10. 2.9 146 km SSW of Adak, Alaska 03:01 UTC
11. 3.3 127 km SSW of Adak, Alaska 02:54 UTC
12. 3.3 120 km SSW of Adak, Alaska 05:40 UTC
13. 1.9 117 km SSW of Adak, Alaska 10:08 UTC
14. 1.6 118 km SW of Adak, Alaska 18:48 UTC
15. 3.8 133 km SW of Adak, Alaska 17:49 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:22 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

• The official USGS event page — the source of record for every value above
• Did you feel it? Report it to USGS — reports go to USGS, not to us
• ShakeMap for this event, when USGS has produced one

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.