31 km ENE 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 it was probably too small to be felt, even directly above it. 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 4.5 on 2016-10-18 — about 11 times the energy of this one.

Before 2016, the USGS record lists 23 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 81 km ENE of Nikolski, Alaska · 49 km ENE of this epicentre Jan 13, 1955
2. 6.6 18 km WSW of Nikolski, Alaska · 50 km WSW of this epicentre Jan 28, 1999
3. 6.2 56 km ENE of Nikolski, Alaska · 26 km NE of this epicentre Sep 4, 1942
4. 6.0 43 km SE of Nikolski, Alaska · 43 km S of this epicentre Apr 3, 1935
5. 6.0 Fox Islands, Aleutian Islands, Alaska · 24 km NE of this epicentre Sep 2, 1942

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 53.0330, -168.4177. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.3 57 km ESE of Nikolski, Alaska 00:19 UTC
2. 3.9 47 km SE of Nikolski, Alaska 13:57 UTC
3. 2.6 66 km NE of Nikolski, Alaska 01:07 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. 2.7 72 km ENE of Nikolski, Alaska 01:08 UTC
7. 4.4 49 km SE of Nikolski, Alaska 06:48 UTC
8. 2.2 58 km ESE of Nikolski, Alaska 19:33 UTC
9. 2.1 25 km S of Nikolski, Alaska 16:26 UTC
10. 2.2 37 km SSE of Nikolski, Alaska 13:12 UTC
11. 2.2 Fox Islands, Aleutian Islands, Alaska 05:26 UTC
12. 2.0 29 km ESE of Nikolski, Alaska 03:39 UTC
13. 2.0 33 km ENE of Nikolski, Alaska 11:34 UTC
14. 2.4 44 km SE of Nikolski, Alaska 13:22 UTC
15. 2.3 15 km SSE of Nikolski, Alaska 10:09 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 13:51 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.