224 km ESE of Atka, 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 82 km (51 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 7.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 22,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,000× the energy of this one
3. Magna, Utah 2020 M 5.7 710× the energy of this one
4. This earthquake M 3.8 about 7.6 tons of TNT
5. Around the size people start to feel M 3.0 this one released 16× 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 5.8 on 2020-08-16 — about 1,000 times the energy of this one.

Before 2016, the USGS record lists 27 earthquakes of M5 or more within 50 km; the five largest:

1. 7.1 Fox Islands, Aleutian Islands, Alaska · 10 km ESE of this epicentre Dec 31, 1901
2. 6.3 240 km SSW of Nikolski, Alaska · 50 km SE of this epicentre Aug 8, 1961
3. 6.2 179 km SW of Nikolski, Alaska · 46 km NE of this epicentre Jun 4, 1956
4. 6.2 Fox Islands, Aleutian Islands, Alaska · 35 km ENE of this epicentre Mar 10, 1957
5. 6.1 207 km ESE of Atka, Alaska · 23 km NNW of this epicentre Mar 13, 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 51.4773, -171.1536. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.3 183 km SW of Nikolski, Alaska 05:58 UTC
2. 3.5 203 km SW of Nikolski, Alaska 01:32 UTC
3. 2.9 187 km ESE of Atka, Alaska 11:13 UTC
4. 3.8 Fox Islands, Aleutian Islands, Alaska 14:03 UTC
5. 2.6 Fox Islands, Aleutian Islands, Alaska 17:44 UTC
6. 2.6 191 km ESE of Atka, Alaska 09:44 UTC
7. 3.7 197 km SW of Nikolski, Alaska 17:10 UTC
8. 3.8 180 km ESE of Atka, Alaska 12:50 UTC
9. 2.9 243 km SSW of Nikolski, Alaska 08:10 UTC
10. 3.0 183 km ESE of Atka, Alaska 21:50 UTC
11. 3.1 182 km SW of Nikolski, Alaska 14:35 UTC
12. 3.1 196 km ESE of Atka, Alaska 12:32 UTC
13. 2.7 Fox Islands, Aleutian Islands, Alaska 11:01 UTC
14. 3.2 193 km SW of Nikolski, Alaska 12:22 UTC
15. 3.7 221 km SSW of Nikolski, Alaska 14:00 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 10:46 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.