238 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 25 km (16 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 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 5.0 on 2016-10-01 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

1. 6.0 195 km S of False Pass, Alaska · 44 km NNW of this epicentre Aug 14, 1924
2. 5.9 228 km S of False Pass, Alaska · 10 km N of this epicentre Oct 13, 1972
3. 5.5 218 km SE of Akutan, Alaska · 45 km WSW of this epicentre May 3, 2010
4. 5.3 223 km S of False Pass, Alaska · 19 km NNE of this epicentre Mar 12, 2015

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 52.7241, -163.0532. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.9 215 km S of False Pass, Alaska 10:45 UTC
2. 3.4 262 km SE of Akutan, Alaska 00:18 UTC
3. 3.2 229 km SE of Akutan, Alaska 08:19 UTC
4. 3.2 245 km S of False Pass, Alaska 22:40 UTC
5. 3.3 244 km SE of Akutan, Alaska 17:15 UTC
6. 3.0 240 km SE of Akutan, Alaska 06:34 UTC
7. 2.8 south of Alaska 11:06 UTC
8. 2.2 228 km SE of Akutan, Alaska 05:25 UTC
9. 3.1 248 km S of False Pass, Alaska 15:29 UTC
10. 3.1 272 km S of False Pass, Alaska 05:40 UTC
11. 2.6 214 km S of False Pass, Alaska 14:35 UTC
12. 2.6 218 km S of False Pass, Alaska 10:06 UTC
13. 3.1 221 km S of False Pass, Alaska 18:21 UTC
14. 2.9 228 km SE of Akutan, Alaska 20:28 UTC
15. 2.5 230 km S of False Pass, Alaska 07:12 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 03:50 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.