73 km S of Nikolski, Alaska

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 261 km (162 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 2.7 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 63× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2.8× the energy of this one
3. Magna, Utah 2020 M 5.7 2× the energy of this one
4. This earthquake M 5.5 about 2.7 kilotons of TNT
5. Around the size people start to feel M 3.0 this one released 5,600× 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 2016-03-27 — about 2.8 times the energy of this one.

Before 2016, the USGS record lists 146 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 46 km SSW of Nikolski, Alaska · 50 km NW of this epicentre Jul 22, 1933
2. 6.8 64 km SSW of Nikolski, Alaska · 50 km WNW of this epicentre Jan 5, 1987
3. 6.7 75 km SSE of Nikolski, Alaska · 20 km E of this epicentre Jan 2, 1957
4. 6.5 96 km SSE of Nikolski, Alaska · 29 km SE of this epicentre Sep 8, 1909
5. 6.5 69 km S of Nikolski, Alaska · 4 km N of this epicentre Aug 12, 1932

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 52.2900, -168.6929. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 58 km S of Nikolski, Alaska 22:55 UTC
2. 2.2 93 km SSE of Nikolski, Alaska 23:21 UTC
3. 1.9 110 km S of Nikolski, Alaska 11:23 UTC
4. 1.8 75 km S of Nikolski, Alaska 10:57 UTC
5. 1.9 87 km S of Nikolski, Alaska 09:11 UTC
6. 1.7 28 km SSE of Nikolski, Alaska 08:11 UTC
7. 2.3 93 km SSE of Nikolski, Alaska 15:36 UTC
8. 1.7 63 km S of Nikolski, Alaska 09:43 UTC
9. 1.7 37 km S of Nikolski, Alaska 20:36 UTC
10. 3.0 87 km S of Nikolski, Alaska 07:18 UTC
11. 2.0 42 km S of Nikolski, Alaska 11:25 UTC
12. 1.5 47 km SE of Nikolski, Alaska 14:53 UTC
13. 3.8 66 km SSE of Nikolski, Alaska 13:57 UTC
14. 1.9 58 km SSW of Nikolski, Alaska 23:49 UTC
15. 1.7 74 km SSW of Nikolski, Alaska 12:44 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:42 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.