200 km W 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 it was probably too small to be felt, even directly above it. 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 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
3. Around the size people start to feel M 3.0 2× the energy of this one
4. This earthquake M 2.8 about 480 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 5.2 on 2016-11-23 — about 4,000 times the energy of this one.

Before 2016, the USGS record lists 20 earthquakes of M5 or more within 50 km; the five largest:

1. 6.6 174 km W of Adak, Alaska · 30 km ESE of this epicentre Apr 16, 2008
2. 6.4 187 km W of Adak, Alaska · 23 km SSE of this epicentre Apr 15, 2008
3. 6.2 230 km W of Adak, Alaska · 30 km W of this epicentre Apr 29, 2007
4. 5.9 194 km W of Adak, Alaska · 48 km S of this epicentre Jun 22, 1978
5. 5.8 224 km W of Adak, Alaska · 34 km SW of this epicentre Jul 5, 1966

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 52.0297, -179.5340. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.9 218 km W of Adak, Alaska 09:09 UTC
2. 2.8 Andreanof Islands, Aleutian Islands, Alaska 07:44 UTC
3. 2.8 Andreanof Islands, Aleutian Islands, Alaska 04:16 UTC
4. 2.1 221 km W of Adak, Alaska 20:16 UTC
5. 2.2 191 km W of Adak, Alaska 08:06 UTC
6. 2.6 229 km W of Adak, Alaska 08:54 UTC
7. 2.3 196 km W of Adak, Alaska 04:57 UTC
8. 2.8 207 km W of Adak, Alaska 20:12 UTC
9. 2.9 225 km W of Adak, Alaska 21:45 UTC
10. 2.5 219 km W of Adak, Alaska 14:49 UTC
11. 2.2 201 km W of Adak, Alaska 11:06 UTC
12. 2.7 202 km W of Adak, Alaska 08:37 UTC
13. 2.5 188 km W of Adak, Alaska 00:20 UTC
14. 3.4 218 km W of Adak, Alaska 08:06 UTC
15. 2.4 177 km W of Adak, Alaska 03:17 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 10:29 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.