159 km S of False Pass, 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 21 km (13 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 5.9 on 2016-10-27 — about 32,000 times the energy of this one.

Before 2016, the USGS record lists 55 earthquakes of M5 or more within 50 km; the five largest:

1. 6.6 146 km ESE of Akutan, Alaska · 18 km NW of this epicentre Apr 1, 1946
2. 6.2 Unimak Island region, Alaska · 46 km NNW of this epicentre Oct 14, 1933
3. 6.2 136 km SE of Akutan, Alaska · 31 km W of this epicentre Apr 1, 1946
4. 6.2 136 km S of False Pass, Alaska · 27 km NNW of this epicentre Apr 2, 1946
5. 6.2 184 km SE of Akutan, Alaska · 27 km SSE of this epicentre Apr 6, 1946

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 53.4238, -163.5961. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.2 155 km S of False Pass, Alaska 22:46 UTC
2. 4.5 151 km S of False Pass, Alaska 22:40 UTC
3. 2.9 150 km S of False Pass, Alaska 21:40 UTC
4. 2.6 169 km ESE of Akutan, Alaska 20:52 UTC
5. 1.9 157 km S of False Pass, Alaska 11:50 UTC
6. 1.9 160 km ESE of Akutan, Alaska 00:09 UTC
7. 2.9 154 km ESE of Akutan, Alaska 01:42 UTC
8. 2.8 157 km S of False Pass, Alaska 18:58 UTC
9. 2.1 145 km S of False Pass, Alaska 14:35 UTC
10. 4.0 155 km ESE of Akutan, Alaska 08:38 UTC
11. 3.8 152 km ESE of Akutan, Alaska 04:12 UTC
12. 2.4 169 km SE of Akutan, Alaska 12:55 UTC
13. 2.1 178 km SE of Akutan, Alaska 22:25 UTC
14. 2.1 151 km ESE of Akutan, Alaska 21:41 UTC
15. 2.0 164 km S of False Pass, Alaska 18:39 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 23:43 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.