132 km SW 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 198 km (123 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 670 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.1 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 250× the energy of this one
2. Mineral, Virginia 2011 M 5.8 11× the energy of this one
3. Magna, Utah 2020 M 5.7 7.9× the energy of this one
4. This earthquake M 5.1 about 670 tons of TNT
5. Around the size people start to feel M 3.0 this one released 1,400× 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 4.5 on 2017-03-07.

Before 2016, the USGS record lists 62 earthquakes of M5 or more within 50 km; the five largest:

1. 6.6 135 km SW of Nikolski, Alaska · 43 km SE of this epicentre Dec 23, 1906
2. 6.0 128 km SW of Nikolski, Alaska · 25 km SE of this epicentre Jun 1, 1945
3. 6.0 164 km WSW of Nikolski, Alaska · 42 km WNW of this epicentre Mar 18, 1957
4. 6.0 161 km WSW of Nikolski, Alaska · 32 km W of this epicentre May 10, 1962
5. 6.0 177 km WSW of Nikolski, Alaska · 45 km WSW of this epicentre Nov 15, 1988

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 52.2843, -170.5004. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.0 138 km SW of Nikolski, Alaska 04:11 UTC
2. 3.4 165 km WSW of Nikolski, Alaska 05:01 UTC
3. 3.0 151 km SW of Nikolski, Alaska 12:02 UTC
4. 2.5 121 km SW of Nikolski, Alaska 19:21 UTC
5. 3.7 123 km SW of Nikolski, Alaska 08:22 UTC
6. 4.4 137 km SW of Nikolski, Alaska 07:39 UTC
7. 4.9 137 km SW of Nikolski, Alaska 08:23 UTC
8. 4.4 123 km SW of Nikolski, Alaska 01:26 UTC
9. 4.9 130 km SW of Nikolski, Alaska 01:22 UTC
10. 2.7 136 km SW of Nikolski, Alaska 09:03 UTC
11. 3.4 129 km SW of Nikolski, Alaska 11:21 UTC
12. 3.6 131 km SW of Nikolski, Alaska 07:33 UTC
13. 2.9 135 km WSW of Nikolski, Alaska 19:39 UTC
14. 2.4 137 km SW of Nikolski, Alaska 11:37 UTC
15. 3.3 133 km WSW of Nikolski, Alaska 11:18 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 17:09 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.