south of Alaska

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 7 km (4 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 120 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.4 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 130,000× the energy of this one
2. Magna, Utah 2020 M 5.7 89,000× the energy of this one
3. Around the size people start to feel M 3.0 7.9× the energy of this one
4. This earthquake M 2.4 about 120 lb of TNT

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 4.8 on 2021-07-29 — about 4,000 times the energy of this one.

Before 2016, the USGS record lists 10 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 164 km SE of Chignik, Alaska · 45 km SW of this epicentre Sep 4, 1989
2. 6.9 143 km ESE of Chignik, Alaska · 31 km NW of this epicentre Feb 13, 1951
3. 6.9 171 km SW of Akhiok, Alaska · 14 km NNE of this epicentre Feb 6, 1964
4. 6.6 128 km SE of Chignik, Alaska · 50 km W of this epicentre Jul 28, 1934
5. 6.2 148 km SSW of Akhiok, Alaska · 48 km ENE of this epicentre Nov 10, 1944

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 55.6086, -155.9339. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.1 south of Alaska 20:02 UTC
2. 2.1 134 km ESE of Chignik, Alaska 00:21 UTC
3. 3.0 168 km SSW of Akhiok, Alaska 18:34 UTC
4. 2.5 144 km SSW of Akhiok, Alaska 05:47 UTC
5. 3.3 149 km SW of Akhiok, Alaska 23:32 UTC
6. 2.3 Alaska Peninsula 23:25 UTC
7. 2.0 148 km SW of Akhiok, Alaska 00:57 UTC
8. 3.0 157 km SW of Akhiok, Alaska 17:43 UTC
9. 2.4 163 km ESE of Chignik, Alaska 15:59 UTC
10. 3.2 152 km SSW of Akhiok, Alaska 08:40 UTC
11. 2.5 165 km ESE of Chignik, Alaska 01:38 UTC
12. 2.5 155 km SW of Akhiok, Alaska 07:19 UTC
13. 2.5 156 km SE of Chignik, Alaska 02:05 UTC
14. 2.2 south of Alaska 03:46 UTC
15. 3.5 157 km SSW of Akhiok, Alaska 10:51 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 02:13 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.