138 km E 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 it was probably too small to be felt, even directly above it. 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 3.8 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.6 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 45,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2,000× the energy of this one
3. Magna, Utah 2020 M 5.7 1,400× the energy of this one
4. This earthquake M 3.6 about 3.8 tons of TNT
5. Around the size people start to feel M 3.0 this one released 7.9× 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 4.9 on 2016-10-20 — about 89 times the energy of this one.

Before 2016, the USGS record lists 12 earthquakes of M5 or more within 50 km; the five largest:

1. 7.3 Fox Islands, Aleutian Islands, Alaska · 45 km SSE of this epicentre Jun 24, 2011
2. 6.9 170 km E of Atka, Alaska · 42 km SE of this epicentre Sep 2, 2011
3. 6.3 143 km E of Atka, Alaska · 43 km S of this epicentre Apr 5, 1957
4. 6.0 182 km E of Atka, Alaska · 48 km ESE of this epicentre Mar 24, 1957
5. 5.8 171 km E of Atka, Alaska · 48 km SE of this epicentre Jun 28, 2011

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 52.3921, -172.2004. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.3 169 km E of Atka, Alaska 22:52 UTC
2. 3.8 104 km ENE of Atka, Alaska 13:09 UTC
3. 3.5 159 km ENE of Atka, Alaska 07:46 UTC
4. 2.6 165 km E of Atka, Alaska 23:42 UTC
5. 3.0 162 km E of Atka, Alaska 03:59 UTC
6. 3.3 139 km E of Atka, Alaska 07:15 UTC
7. 5.0 129 km E of Atka, Alaska 06:47 UTC
8. 3.6 164 km E of Atka, Alaska 19:13 UTC
9. 2.6 153 km E of Atka, Alaska 07:24 UTC
10. 5.0 172 km ENE of Atka, Alaska 15:01 UTC
11. 3.5 173 km E of Atka, Alaska 23:42 UTC
12. 3.8 132 km ENE of Atka, Alaska 02:45 UTC
13. 3.7 107 km E of Atka, Alaska 15:20 UTC
14. 3.7 147 km ENE of Atka, Alaska 17:04 UTC
15. 3.5 137 km E of Atka, Alaska 10:16 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:54 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.