224 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 17 earthquakes of M5 or more within 50 km; the five largest:

1. 6.4 187 km W of Adak, Alaska · 40 km ESE of this epicentre Apr 15, 2008
2. 6.2 230 km W of Adak, Alaska · 5 km W of this epicentre Apr 29, 2007
3. 5.8 224 km W of Adak, Alaska · 21 km S of this epicentre Jul 5, 1966
4. 5.8 184 km W of Adak, Alaska · 43 km ESE of this epicentre Mar 2, 2008
5. 5.7 229 km W of Adak, Alaska · 7 km NW of this epicentre Aug 11, 1968

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 52.0002, -179.8968. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.6 225 km W of Adak, Alaska 00:49 UTC
2. 1.6 222 km W of Adak, Alaska 10:55 UTC
3. 2.5 192 km W of Adak, Alaska 15:57 UTC
4. 2.9 217 km W of Adak, Alaska 19:53 UTC
5. 1.8 228 km W of Adak, Alaska 16:07 UTC
6. 2.0 226 km W of Adak, Alaska 13:35 UTC
7. 2.7 231 km W of Adak, Alaska 22:40 UTC
8. 1.7 194 km W of Adak, Alaska 19:17 UTC
9. 2.9 232 km W of Adak, Alaska 15:34 UTC
10. 2.0 211 km W of Adak, Alaska 08:24 UTC
11. 2.8 192 km W of Adak, Alaska 12:14 UTC
12. 1.7 204 km W of Adak, Alaska 02:57 UTC
13. 1.9 219 km W of Adak, Alaska 17:06 UTC
14. 1.8 216 km W of Adak, Alaska 05:45 UTC
15. 2.3 221 km W of Adak, Alaska 07:04 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:17 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.