135 km SE of Atka, Alaska

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 138 km (86 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 85 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 2,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 89× the energy of this one
3. Magna, Utah 2020 M 5.7 63× the energy of this one
4. This earthquake M 4.5 about 85 tons of TNT
5. Around the size people start to feel M 3.0 this one released 180× 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 2016-11-20.

Before 2016, the USGS record lists 36 earthquakes of M5 or more within 50 km; the five largest:

1. 6.5 95 km ESE of Atka, Alaska · 44 km NNW of this epicentre Mar 10, 1957
2. 6.5 99 km SE of Atka, Alaska · 37 km NW of this epicentre Nov 9, 2015
3. 6.1 108 km SE of Atka, Alaska · 32 km NNW of this epicentre May 1, 1933
4. 6.1 109 km SE of Atka, Alaska · 30 km NNW of this epicentre Jul 17, 1985
5. 6.1 96 km SE of Atka, Alaska · 39 km NW of this epicentre Sep 14, 1998

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 51.3755, -172.7419. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.0 99 km ESE of Atka, Alaska 23:54 UTC
2. 3.2 123 km SE of Atka, Alaska 22:33 UTC
3. 3.3 140 km SE of Atka, Alaska 07:57 UTC
4. 3.5 121 km SE of Atka, Alaska 15:54 UTC
5. 3.7 126 km ESE of Atka, Alaska 13:23 UTC
6. 3.0 89 km SE of Atka, Alaska 10:12 UTC
7. 2.7 145 km SE of Atka, Alaska 20:23 UTC
8. 3.0 151 km SSE of Atka, Alaska 13:35 UTC
9. 2.1 111 km ESE of Atka, Alaska 12:34 UTC
10. 2.8 119 km ESE of Atka, Alaska 09:16 UTC
11. 3.0 97 km SE of Atka, Alaska 04:24 UTC
12. 3.2 96 km SE of Atka, Alaska 10:49 UTC
13. 3.7 89 km SE of Atka, Alaska 13:11 UTC
14. 2.1 119 km SE of Atka, Alaska 08:58 UTC
15. 3.5 107 km ESE of Atka, Alaska 22:54 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:26 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.