210 km SSE of Akutan, 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

1. 5.4 219 km SSE of Unalaska, Alaska · 37 km SW of this epicentre Jun 18, 1973
2. 5.1 200 km SE of Akutan, Alaska · 40 km NE of this epicentre Jul 8, 1989
3. 5.1 162 km SSE of Akutan, Alaska · 49 km NNW of this epicentre Apr 28, 1996

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 52.4047, -164.4811. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.7 216 km SSE of Akutan, Alaska 02:28 UTC
2. 2.6 190 km SSE of Unalaska, Alaska 17:02 UTC
3. 2.2 225 km SE of Unalaska, Alaska 09:14 UTC
4. 2.3 168 km SSE of Akutan, Alaska 12:28 UTC
5. 2.4 176 km SE of Unalaska, Alaska 19:51 UTC
6. 3.1 207 km SSE of Unalaska, Alaska 08:09 UTC
7. 3.4 203 km SSE of Unalaska, Alaska 16:55 UTC
8. 2.3 200 km SSE of Akutan, Alaska 07:52 UTC
9. 2.4 172 km SE of Unalaska, Alaska 02:12 UTC
10. 3.1 215 km SE of Unalaska, Alaska 01:21 UTC
11. 2.1 171 km SE of Unalaska, Alaska 09:19 UTC
12. 2.2 178 km SSE of Akutan, Alaska 04:04 UTC
13. 3.6 202 km SSE of Unalaska, Alaska 11:43 UTC
14. 2.9 193 km SE of Akutan, Alaska 23:48 UTC
15. 2.6 210 km SSE of Akutan, Alaska 01:48 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 22:52 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.