129 km SSW of Nikolski, 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 69 km (43 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 3.8 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.6 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 45,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2,000× the energy of this one
3. Magna, Utah 2020 M 5.7 1,400× the energy of this one
4. This earthquake M 3.6 about 3.8 tons of TNT
5. Around the size people start to feel M 3.0 this one released 7.9× 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 5.5 on 2020-09-27 — about 710 times the energy of this one.

Before 2016, the USGS record lists 75 earthquakes of M5 or more within 50 km; the five largest:

1. 6.0 119 km SSW of Nikolski, Alaska · 33 km NW of this epicentre Mar 29, 1931
2. 6.0 101 km SSW of Nikolski, Alaska · 34 km NNW of this epicentre Feb 9, 1953
3. 6.0 100 km SSW of Nikolski, Alaska · 41 km NNW of this epicentre Mar 24, 1957
4. 6.0 116 km SSW of Nikolski, Alaska · 26 km NW of this epicentre Dec 13, 1957
5. 6.0 107 km SSW of Nikolski, Alaska · 24 km N of this epicentre Jan 8, 1990

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 51.8217, -169.3909. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.8 108 km SSW of Nikolski, Alaska 02:34 UTC
2. 3.0 120 km SSW of Nikolski, Alaska 21:41 UTC
3. 2.5 105 km SSW of Nikolski, Alaska 10:22 UTC
4. 2.2 109 km SSW of Nikolski, Alaska 01:20 UTC
5. 2.7 Fox Islands, Aleutian Islands, Alaska 22:50 UTC
6. 2.7 83 km SSW of Nikolski, Alaska 09:04 UTC
7. 2.6 107 km SSW of Nikolski, Alaska 12:18 UTC
8. 3.9 Fox Islands, Aleutian Islands, Alaska 20:26 UTC
9. 4.3 85 km SSW of Nikolski, Alaska 06:38 UTC
10. 4.2 97 km SSW of Nikolski, Alaska 01:20 UTC
11. 1.9 100 km SW of Nikolski, Alaska 00:22 UTC
12. 2.0 98 km SSW of Nikolski, Alaska 21:45 UTC
13. 2.2 99 km SSW of Nikolski, Alaska 20:39 UTC
14. 2.1 88 km SSW of Nikolski, Alaska 03:50 UTC
15. 2.6 88 km S of Nikolski, Alaska 10:19 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 20:33 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.