208 km SSE of Atka, 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 204 km (127 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 4.2 on 2017-11-29.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

1. 6.9 182 km SSE of Atka, Alaska · 26 km NNW of this epicentre Jan 27, 1906
2. 6.2 234 km SSE of Atka, Alaska · 41 km SSW of this epicentre Mar 20, 1958
3. 5.8 174 km SSE of Atka, Alaska · 39 km NW of this epicentre Apr 1, 1957
4. 5.8 161 km SSE of Atka, Alaska · 49 km NW of this epicentre Apr 2, 1957
5. 5.8 165 km SSE of Atka, Alaska · 48 km NW of this epicentre Apr 2, 1957

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 50.6010, -172.6287. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.3 201 km SSE of Atka, Alaska 13:33 UTC
2. 4.6 188 km SSE of Atka, Alaska 20:41 UTC
3. 3.8 187 km SSE of Atka, Alaska 06:46 UTC
4. 3.2 169 km SSE of Atka, Alaska 13:54 UTC
5. 3.3 213 km SE of Atka, Alaska 06:03 UTC
6. 3.7 195 km SE of Atka, Alaska 04:01 UTC
7. 3.8 176 km SSE of Atka, Alaska 14:08 UTC
8. 3.1 205 km SSE of Atka, Alaska 13:14 UTC
9. 3.7 176 km SSE of Atka, Alaska 02:25 UTC
10. 3.0 228 km SSE of Atka, Alaska 16:21 UTC
11. 2.8 177 km SSE of Atka, Alaska 19:36 UTC
12. 2.9 189 km SSE of Atka, Alaska 17:14 UTC
13. 3.5 206 km SSE of Atka, Alaska 16:29 UTC
14. 2.9 182 km SSE of Atka, Alaska 17:21 UTC
15. 2.9 199 km SSE of Atka, Alaska 06:43 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 12:29 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.