204 km SSE 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 45 km (28 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 1,900 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.2 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 180,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 7,900× the energy of this one
3. Magna, Utah 2020 M 5.7 5,600× the energy of this one
4. This earthquake M 3.2 about 1,900 lb of TNT
5. Around the size people start to feel M 3.0 this one released 2× 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 5.1 on 2023-01-26 — about 710 times the energy of this one.

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 · 24 km N of this epicentre Jan 27, 1906
2. 6.2 234 km SSE of Atka, Alaska · 38 km SSW of this epicentre Mar 20, 1958
3. 5.8 174 km SSE of Atka, Alaska · 32 km NW of this epicentre Apr 1, 1957
4. 5.8 161 km SSE of Atka, Alaska · 44 km NW of this epicentre Apr 2, 1957
5. 5.8 165 km SSE of Atka, Alaska · 41 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 50.5967, -172.7565. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.9 199 km SSE of Atka, Alaska 06:43 UTC
2. 2.6 189 km SSE of Atka, Alaska 04:03 UTC
3. 2.9 184 km SSE of Atka, Alaska 17:39 UTC
4. 2.3 193 km SE of Atka, Alaska 01:21 UTC
5. 3.6 209 km SSE of Atka, Alaska 22:26 UTC
6. 3.4 183 km SSE of Atka, Alaska 23:50 UTC
7. 3.5 232 km SSE of Atka, Alaska 04:30 UTC
8. 2.4 162 km SSE of Atka, Alaska 09:23 UTC
9. 2.9 191 km SSE of Atka, Alaska 07:15 UTC
10. 2.9 185 km SSE of Atka, Alaska 18:31 UTC
11. 2.8 163 km SSE of Atka, Alaska 18:35 UTC
12. 3.4 214 km SSE of Atka, Alaska 09:49 UTC
13. 2.9 181 km SSE of Atka, Alaska 21:16 UTC
14. 3.9 198 km SSE of Atka, Alaska 18:21 UTC
15. 3.8 184 km SSE of Atka, Alaska 22:21 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:55 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.