184 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 950 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.0 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 350,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 16,000× the energy of this one
3. Magna, Utah 2020 M 5.7 11,000× the energy of this one
4. This earthquake M 3.0 about 950 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 5.3 on 2023-02-15 — about 2,800 times the energy of this one.

Before 2016, the USGS record lists 109 earthquakes of M5 or more within 50 km; the five largest:

1. 7.2 162 km WSW of Adak, Alaska · 38 km SE of this epicentre Mar 16, 1957
2. 7.2 207 km WSW of Adak, Alaska · 36 km SSW of this epicentre Dec 19, 2007
3. 6.9 203 km WSW of Adak, Alaska · 34 km SSW of this epicentre Mar 31, 1913
4. 6.8 177 km WSW of Adak, Alaska · 41 km SSE of this epicentre Oct 7, 1989
5. 6.7 205 km WSW of Adak, Alaska · 23 km WSW 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 51.6455, -179.2775. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.0 163 km WSW of Adak, Alaska 00:00 UTC
2. 1.8 214 km WSW of Adak, Alaska 21:58 UTC
3. 2.6 149 km WSW of Adak, Alaska 11:55 UTC
4. 1.8 165 km WSW of Adak, Alaska 10:29 UTC
5. 3.1 216 km WSW of Adak, Alaska 09:36 UTC
6. 1.8 216 km W of Adak, Alaska 05:45 UTC
7. 1.8 208 km WSW of Adak, Alaska 01:23 UTC
8. 1.8 186 km WSW of Adak, Alaska 16:00 UTC
9. 1.8 168 km W of Adak, Alaska 12:39 UTC
10. 1.9 195 km WSW of Adak, Alaska 15:32 UTC
11. 2.1 166 km W of Adak, Alaska 05:58 UTC
12. 2.0 167 km W of Adak, Alaska 05:57 UTC
13. 2.0 167 km W of Adak, Alaska 15:35 UTC
14. 3.1 169 km W of Adak, Alaska 15:16 UTC
15. 2.9 168 km W of Adak, Alaska 22:40 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:24 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.