156 km ESE of Atka, Alaska

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 53 km (33 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 2.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 63,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2,800× the energy of this one
3. Magna, Utah 2020 M 5.7 2,000× the energy of this one
4. This earthquake M 3.5 about 2.7 tons of TNT
5. Around the size people start to feel M 3.0 this one released 5.6× 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 2016-08-14 — about 32 times the energy of this one.

Before 2016, the USGS record lists 31 earthquakes of M5 or more within 50 km; the five largest:

1. 7.3 Fox Islands, Aleutian Islands, Alaska · 22 km NNE of this epicentre Jun 24, 2011
2. 6.9 170 km E of Atka, Alaska · 38 km NNE of this epicentre Sep 2, 2011
3. 6.5 143 km ESE of Atka, Alaska · 23 km SW of this epicentre Oct 14, 1960
4. 6.3 143 km E of Atka, Alaska · 19 km NW of this epicentre Apr 5, 1957
5. 6.1 185 km ESE of Atka, Alaska · 28 km E of this epicentre Dec 6, 1930

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 51.8723, -171.9740. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.9 179 km ESE of Atka, Alaska 06:19 UTC
2. 2.3 135 km ESE of Atka, Alaska 16:51 UTC
3. 3.4 182 km E of Atka, Alaska 08:35 UTC
4. 3.2 150 km ESE of Atka, Alaska 22:08 UTC
5. 3.3 Andreanof Islands, Aleutian Islands, Alaska 06:35 UTC
6. 3.1 183 km ESE of Atka, Alaska 13:52 UTC
7. 2.8 176 km ESE of Atka, Alaska 12:53 UTC
8. 2.8 119 km E of Atka, Alaska 16:47 UTC
9. 2.8 188 km E of Atka, Alaska 10:38 UTC
10. 3.6 122 km E of Atka, Alaska 19:20 UTC
11. 3.2 131 km E of Atka, Alaska 02:56 UTC
12. 1.9 170 km E of Atka, Alaska 02:07 UTC
13. 2.2 173 km ESE of Atka, Alaska 12:17 UTC
14. 2.1 176 km ESE of Atka, Alaska 06:28 UTC
15. 3.5 135 km E of Atka, Alaska 01:43 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:16 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.