208 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, people at rest would likely notice it out to about 49 km (30 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 1.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 130,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 5,600× the energy of this one
3. Magna, Utah 2020 M 5.7 4,000× the energy of this one
4. This earthquake M 3.3 about 1.3 tons of TNT
5. Around the size people start to feel M 3.0 this one released 2.8× more

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 6.1 on 2021-01-03 — about 16,000 times the energy of this one.

Before 2016, the USGS record lists 96 earthquakes of M5 or more within 50 km; the five largest:

1. 7.2 207 km WSW of Adak, Alaska · 29 km SSE of this epicentre Dec 19, 2007
2. 6.9 203 km WSW of Adak, Alaska · 31 km SSE of this epicentre Mar 31, 1913
3. 6.9 231 km WSW of Adak, Alaska · 38 km SSW of this epicentre May 14, 1969
4. 6.8 235 km WSW of Adak, Alaska · 42 km SSW of this epicentre May 6, 1987
5. 6.7 237 km WSW of Adak, Alaska · 37 km SW of this epicentre Oct 13, 1926

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 51.6142, -179.6307. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.3 212 km W of Adak, Alaska 23:53 UTC
2. 3.3 233 km WSW of Adak, Alaska 09:16 UTC
3. 2.6 190 km WSW of Adak, Alaska 04:25 UTC
4. 3.0 182 km WSW of Adak, Alaska 15:56 UTC
5. 3.1 193 km W of Adak, Alaska 16:03 UTC
6. 2.6 Andreanof Islands, Aleutian Islands, Alaska 00:14 UTC
7. 2.6 214 km WSW of Adak, Alaska 17:10 UTC
8. 2.0 206 km WSW of Adak, Alaska 08:54 UTC
9. 2.5 Andreanof Islands, Aleutian Islands, Alaska 12:25 UTC
10. 2.3 211 km WSW of Adak, Alaska 23:25 UTC
11. 2.3 212 km W of Adak, Alaska 00:08 UTC
12. 4.2 210 km WSW of Adak, Alaska 13:07 UTC
13. 2.4 228 km WSW of Adak, Alaska 05:50 UTC
14. 3.1 181 km W of Adak, Alaska 23:53 UTC
15. 3.3 204 km WSW of Adak, Alaska 17:12 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:34 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.