229 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 1,300 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 250,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 11,000× the energy of this one
3. Magna, Utah 2020 M 5.7 7,900× the energy of this one
4. This earthquake M 3.1 about 1,300 lb of TNT
5. Around the size people start to feel M 3.0 this one released 1.4× 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 1,400 times the energy of this one.

Before 2016, the USGS record lists 34 earthquakes of M5 or more within 50 km; the five largest:

1. 6.7 237 km WSW of Adak, Alaska · 44 km S of this epicentre Oct 13, 1926
2. 6.7 205 km WSW of Adak, Alaska · 35 km SE of this epicentre Oct 13, 1926
3. 6.7 227 km WSW of Adak, Alaska · 38 km SSE of this epicentre Jun 2, 1955
4. 6.7 221 km WSW of Adak, Alaska · 29 km SSE of this epicentre Jun 20, 1955
5. 6.7 239 km WSW of Adak, Alaska · 49 km S of this epicentre Aug 2, 2007

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 51.7478, -179.9559. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.7 212 km W of Adak, Alaska 13:14 UTC
2. 2.3 195 km W of Adak, Alaska 18:54 UTC
3. 2.0 224 km WSW of Adak, Alaska 11:17 UTC
4. 2.9 203 km W of Adak, Alaska 23:37 UTC
5. 2.7 213 km W of Adak, Alaska 16:00 UTC
6. 2.8 215 km W of Adak, Alaska 14:59 UTC
7. 2.1 222 km W of Adak, Alaska 11:41 UTC
8. 2.2 206 km W of Adak, Alaska 05:08 UTC
9. 3.3 195 km W of Adak, Alaska 05:44 UTC
10. 2.0 200 km WSW of Adak, Alaska 12:55 UTC
11. 2.2 224 km W of Adak, Alaska 04:24 UTC
12. 2.4 217 km W of Adak, Alaska 03:35 UTC
13. 3.3 206 km W of Adak, Alaska 01:01 UTC
14. 2.2 220 km WSW of Adak, Alaska 23:04 UTC
15. 2.3 214 km W of Adak, Alaska 14:53 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 08:09 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.