77 km SW of Nikolski, Alaska

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 142 km (88 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 120 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.6 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 1,400× the energy of this one
2. Mineral, Virginia 2011 M 5.8 63× the energy of this one
3. Magna, Utah 2020 M 5.7 45× the energy of this one
4. This earthquake M 4.6 about 120 tons of TNT
5. Around the size people start to feel M 3.0 this one released 250× 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 4.9 on 2016-04-02 — about 2.8 times the energy of this one.

Before 2016, the USGS record lists 99 earthquakes of M5 or more within 50 km; the five largest:

1. 7.1 35 km SW of Nikolski, Alaska · 43 km ENE of this epicentre Mar 11, 1957
2. 6.9 77 km SSW of Nikolski, Alaska · 28 km SE of this epicentre Jan 23, 1935
3. 6.9 80 km SW of Nikolski, Alaska · 20 km SE of this epicentre Mar 9, 1957
4. 6.9 Fox Islands, Aleutian Islands, Alaska · 24 km ESE of this epicentre Jul 27, 2015
5. 6.8 46 km SSW of Nikolski, Alaska · 36 km ENE of this epicentre Jul 22, 1933

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 52.4908, -169.7436. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.5 58 km SW of Nikolski, Alaska 15:33 UTC
2. 2.6 83 km SW of Nikolski, Alaska 20:27 UTC
3. 2.5 122 km SW of Nikolski, Alaska 20:19 UTC
4. 3.1 126 km SW of Nikolski, Alaska 20:11 UTC
5. 2.0 55 km SW of Nikolski, Alaska 12:42 UTC
6. 2.2 70 km SSW of Nikolski, Alaska 08:58 UTC
7. 2.3 Fox Islands, Aleutian Islands, Alaska 13:29 UTC
8. 2.1 47 km WSW of Nikolski, Alaska 07:11 UTC
9. 2.0 70 km WSW of Nikolski, Alaska 01:37 UTC
10. 3.1 83 km SW of Nikolski, Alaska 11:38 UTC
11. 3.4 78 km SSW of Nikolski, Alaska 09:03 UTC
12. 2.5 70 km SW of Nikolski, Alaska 06:53 UTC
13. 2.3 49 km SW of Nikolski, Alaska 00:38 UTC
14. 2.3 80 km SSW of Nikolski, Alaska 21:15 UTC
15. 2.2 51 km SSW of Nikolski, Alaska 16:36 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 17:18 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.