144 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 6.2 on 2017-05-08 — about 130,000 times the energy of this one.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

1. 6.6 174 km W of Adak, Alaska · 42 km SW of this epicentre Apr 16, 2008
2. 6.4 170 km WNW of Adak, Alaska · 41 km NNW of this epicentre Mar 13, 1992
3. 6.3 128 km W of Adak, Alaska · 21 km SE of this epicentre May 10, 1939
4. 6.2 146 km WNW of Adak, Alaska · 7 km NNW of this epicentre Mar 22, 2008
5. 5.9 109 km WNW of Adak, Alaska · 45 km ENE of this epicentre Aug 5, 1940

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 52.1181, -178.6935. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.2 107 km W of Adak, Alaska 10:57 UTC
2. 2.0 124 km W of Adak, Alaska 18:34 UTC
3. 3.9 150 km WNW of Adak, Alaska 04:37 UTC
4. 1.9 132 km W of Adak, Alaska 01:35 UTC
5. 4.0 169 km WNW of Adak, Alaska 08:07 UTC
6. 1.9 140 km W of Adak, Alaska 16:48 UTC
7. 1.6 105 km W of Adak, Alaska 09:03 UTC
8. 3.7 184 km WNW of Adak, Alaska 20:43 UTC
9. 3.0 166 km W of Adak, Alaska 16:31 UTC
10. 2.2 141 km W of Adak, Alaska 05:46 UTC
11. 1.9 137 km W of Adak, Alaska 12:46 UTC
12. 3.4 145 km W of Adak, Alaska 06:27 UTC
13. 3.3 135 km WNW of Adak, Alaska 16:52 UTC
14. 2.5 133 km W of Adak, Alaska 05:31 UTC
15. 1.8 122 km W of Adak, Alaska 13:15 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 11:24 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.