231 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 2.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 63,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2,800× the energy of this one
3. Magna, Utah 2020 M 5.7 2,000× the energy of this one
4. This earthquake M 3.5 about 2.7 tons of TNT
5. Around the size people start to feel M 3.0 this one released 5.6× 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 5.2 on 2016-11-23 — about 350 times the energy of this one.

Before 2016, the USGS record lists 25 earthquakes of M5 or more within 50 km; the five largest:

1. 6.7 205 km WSW of Adak, Alaska · 42 km SE of this epicentre Oct 13, 1926
2. 6.7 227 km WSW of Adak, Alaska · 45 km SSE of this epicentre Jun 2, 1955
3. 6.7 221 km WSW of Adak, Alaska · 36 km SSE of this epicentre Jun 20, 1955
4. 6.4 187 km W of Adak, Alaska · 44 km E of this epicentre Apr 15, 2008
5. 6.2 Andreanof Islands, Aleutian Islands, Alaska · 49 km SSE of this epicentre Mar 10, 1957

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 51.8115, -179.9987. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.8 212 km W of Adak, Alaska 15:17 UTC
2. 3.3 206 km W of Adak, Alaska 17:42 UTC
3. 2.8 204 km W of Adak, Alaska 15:18 UTC
4. 2.2 201 km W of Adak, Alaska 09:47 UTC
5. 2.1 198 km W of Adak, Alaska 22:11 UTC
6. 2.7 227 km W of Adak, Alaska 15:34 UTC
7. 1.9 218 km W of Adak, Alaska 14:58 UTC
8. 2.6 209 km W of Adak, Alaska 06:09 UTC
9. 1.8 230 km W of Adak, Alaska 13:10 UTC
10. 1.9 214 km W of Adak, Alaska 19:31 UTC
11. 1.7 213 km W of Adak, Alaska 06:59 UTC
12. 2.8 233 km WSW of Adak, Alaska 11:21 UTC
13. 2.7 227 km W of Adak, Alaska 17:26 UTC
14. 2.0 200 km W of Adak, Alaska 07:15 UTC
15. 2.0 195 km W of Adak, Alaska 23:24 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:18 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.