55 km SE 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 6 km (4 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 680 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 22,000× the energy of this one
2. Magna, Utah 2020 M 5.7 16,000× the energy of this one
3. Around the size people start to feel M 3.0 1.4× the energy of this one
4. This earthquake M 2.9 about 680 lb of TNT

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 2016-03-28 — about 7,900 times the energy of this one.

Before 2016, the USGS record lists 118 earthquakes of M5 or more within 50 km; the five largest:

1. 6.7 103 km SE of Nikolski, Alaska · 47 km ESE of this epicentre Feb 20, 1916
2. 6.7 75 km SSE of Nikolski, Alaska · 37 km SSW of this epicentre Jan 2, 1957
3. 6.7 72 km ESE of Nikolski, Alaska · 22 km ENE of this epicentre Jan 2, 1957
4. 6.6 61 km SE of Nikolski, Alaska · 6 km SE of this epicentre Jan 2, 1957
5. 6.5 69 km S of Nikolski, Alaska · 47 km SW 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 52.6295, -168.2097. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.3 89 km SSE of Nikolski, Alaska 11:54 UTC
2. 2.4 55 km SSE of Nikolski, Alaska 10:49 UTC
3. 2.5 72 km E of Nikolski, Alaska 19:37 UTC
4. 2.4 44 km ESE of Nikolski, Alaska 02:28 UTC
5. 2.3 50 km SE of Nikolski, Alaska 11:17 UTC
6. 4.4 49 km SE of Nikolski, Alaska 06:48 UTC
7. 2.3 101 km SE of Nikolski, Alaska 07:34 UTC
8. 2.2 58 km ESE of Nikolski, Alaska 19:33 UTC
9. 3.6 89 km SE of Nikolski, Alaska 07:28 UTC
10. 4.4 91 km SE of Nikolski, Alaska 17:53 UTC
11. 2.2 37 km SSE of Nikolski, Alaska 13:12 UTC
12. 2.0 80 km SE of Nikolski, Alaska 01:36 UTC
13. 2.2 Fox Islands, Aleutian Islands, Alaska 05:26 UTC
14. 2.2 80 km E of Nikolski, Alaska 22:24 UTC
15. 2.0 78 km E of Nikolski, Alaska 16:23 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:05 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.