285 km SW 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 4.7 on 2022-04-12 — about 500 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

1. 6.7 254 km SW of Adak, Alaska · 46 km N of this epicentre Sep 14, 1905
2. 6.0 254 km SW of Adak, Alaska · 47 km E of this epicentre Jul 8, 1929
3. 6.0 257 km SW of Adak, Alaska · 36 km E of this epicentre Jul 3, 1957
4. 6.0 295 km SW of Adak, Alaska · 18 km W of this epicentre Feb 27, 1970
5. 5.6 289 km SW of Adak, Alaska · 13 km WNW of this epicentre Mar 27, 1974

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 50.0516, -179.4951. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.6 250 km SW of Adak, Alaska 15:50 UTC
2. 2.6 south of the Aleutian Islands 01:55 UTC
3. 3.6 265 km SW of Adak, Alaska 22:18 UTC
4. 2.7 283 km SW of Adak, Alaska 03:31 UTC
5. 3.5 276 km SW of Adak, Alaska 05:09 UTC
6. 2.7 247 km SW of Adak, Alaska 21:54 UTC
7. 3.6 Andreanof Islands, Aleutian Islands, Alaska 21:55 UTC
8. 3.1 290 km SW of Adak, Alaska 09:34 UTC
9. 2.9 289 km SW of Adak, Alaska 05:05 UTC
10. 3.2 275 km SW of Adak, Alaska 08:59 UTC
11. 2.8 263 km SW of Adak, Alaska 19:26 UTC
12. 3.0 Andreanof Islands, Aleutian Islands, Alaska 23:04 UTC
13. 3.0 295 km SW of Adak, Alaska 23:32 UTC
14. 2.2 292 km SW of Adak, Alaska 15:22 UTC
15. 3.7 269 km SW of Adak, Alaska 04:02 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 16:52 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.