86 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 310 km (193 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 7.6 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.8 would have released about 32 times as much.

1. Ridgecrest, California 2019 M 7.1 89× the energy of this one
2. Loma Prieta, California 1989 M 6.9 45× the energy of this one
3. Northridge, California 1994 M 6.7 22× the energy of this one
4. This earthquake M 5.8 about 7.6 kilotons of TNT
5. Magna, Utah 2020 M 5.7 this one released 1.4× more
6. Around the size people start to feel M 3.0 this one released 16,000× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.1 on 2016-01-21.

Before 2016, the USGS record lists 129 earthquakes of M5 or more within 50 km; the five largest:

1. 6.7 75 km SSE of Nikolski, Alaska · 24 km NE of this epicentre Jan 2, 1957
2. 6.5 96 km SSE of Nikolski, Alaska · 21 km ESE of this epicentre Sep 8, 1909
3. 6.5 69 km S of Nikolski, Alaska · 17 km N of this epicentre Aug 12, 1932
4. 6.5 45 km SSE of Nikolski, Alaska · 44 km N of this epicentre Jan 2, 1957
5. 6.5 85 km SSE of Nikolski, Alaska · 22 km ENE of this epicentre Dec 21, 1962

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 52.1750, -168.6554. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.1 92 km SSE of Nikolski, Alaska 14:26 UTC
2. 2.2 101 km SSE of Nikolski, Alaska 13:26 UTC
3. 3.9 66 km SSE of Nikolski, Alaska 19:03 UTC
4. 3.9 89 km SSE of Nikolski, Alaska 19:00 UTC
5. 4.7 73 km SSE of Nikolski, Alaska 10:18 UTC
6. 2.2 64 km SSE of Nikolski, Alaska 01:28 UTC
7. 2.2 45 km SSE of Nikolski, Alaska 13:27 UTC
8. 2.3 99 km SSE of Nikolski, Alaska 06:38 UTC
9. 2.1 89 km SSE of Nikolski, Alaska 20:57 UTC
10. 1.9 55 km SSW of Nikolski, Alaska 17:28 UTC
11. 2.5 87 km SSW of Nikolski, Alaska 17:32 UTC
12. 3.7 86 km SSE of Nikolski, Alaska 06:16 UTC
13. 2.7 86 km S of Nikolski, Alaska 13:58 UTC
14. 3.8 84 km SSE of Nikolski, Alaska 19:27 UTC
15. 2.7 88 km S of Nikolski, Alaska 10:15 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:24 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.