67 km ESE of Chignik, 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 20 km (12 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 5.7 on 2021-07-29 — about 89,000 times the energy of this one.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 113 km ESE of Chignik, Alaska · 49 km SE of this epicentre May 4, 1923
2. 6.5 60 km ENE of Chignik, Alaska · 42 km NNW of this epicentre Sep 28, 1941
3. 6.4 77 km ESE of Chignik, Alaska · 11 km E of this epicentre Mar 24, 1972
4. 6.3 112 km E of Chignik, Alaska · 47 km E of this epicentre Feb 25, 1953
5. 5.7 71 km ENE of Chignik, Alaska · 44 km N of this epicentre Feb 7, 1967

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 56.1298, -157.3617. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.7 46 km ENE of Chignik, Alaska 07:39 UTC
2. 1.8 47 km E of Chignik, Alaska 03:12 UTC
3. 2.2 80 km E of Chignik, Alaska 21:22 UTC
4. 2.0 40 km E of Chignik, Alaska 15:45 UTC
5. 2.1 44 km ESE of Chignik, Alaska 06:55 UTC
6. 2.3 48 km E of Chignik, Alaska 10:42 UTC
7. 1.7 39 km SE of Chignik, Alaska 21:14 UTC
8. 1.8 76 km ESE of Chignik, Alaska 15:10 UTC
9. 2.4 55 km E of Chignik, Alaska 04:18 UTC
10. 2.6 45 km E of Chignik, Alaska 00:14 UTC
11. 2.3 64 km ESE of Chignik, Alaska 08:10 UTC
12. 2.3 73 km ESE of Chignik, Alaska 21:21 UTC
13. 1.8 37 km ESE of Chignik, Alaska 13:50 UTC
14. 2.5 44 km ESE of Chignik, Alaska 08:12 UTC
15. 2.4 85 km ESE of Chignik, Alaska 00:55 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:57 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.