211 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 51 earthquakes of M5 or more within 50 km; the five largest:

1. 7.2 207 km WSW of Adak, Alaska · 44 km SSE of this epicentre Dec 19, 2007
2. 6.9 203 km WSW of Adak, Alaska · 46 km SSE of this epicentre Mar 31, 1913
3. 6.7 237 km WSW of Adak, Alaska · 47 km SSW of this epicentre Oct 13, 1926
4. 6.7 205 km WSW of Adak, Alaska · 24 km SSE of this epicentre Oct 13, 1926
5. 6.7 227 km WSW of Adak, Alaska · 38 km SSW of this epicentre Jun 2, 1955

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 51.7418, -179.6886. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.6 202 km WSW of Adak, Alaska 12:03 UTC
2. 1.7 188 km WSW of Adak, Alaska 08:53 UTC
3. 2.0 206 km WSW of Adak, Alaska 00:07 UTC
4. 3.1 229 km W of Adak, Alaska 14:49 UTC
5. 2.7 228 km W of Adak, Alaska 01:42 UTC
6. 3.4 184 km W of Adak, Alaska 13:15 UTC
7. 1.8 175 km W of Adak, Alaska 11:33 UTC
8. 2.6 209 km W of Adak, Alaska 20:56 UTC
9. 1.9 208 km W of Adak, Alaska 10:23 UTC
10. 2.0 208 km WSW of Adak, Alaska 05:45 UTC
11. 1.6 196 km WSW of Adak, Alaska 03:05 UTC
12. 3.3 195 km WSW of Adak, Alaska 09:28 UTC
13. 2.7 233 km WSW of Adak, Alaska 12:42 UTC
14. 2.2 226 km WSW of Adak, Alaska 10:17 UTC
15. 2.7 226 km WSW of Adak, Alaska 10:16 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:25 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.