82 km E of Chignik, 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 11 km (7 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 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
3. Around the size people start to feel M 3.0 5.6× the energy of this one
4. This earthquake M 2.5 about 170 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 6.9 on 2021-10-11 — about 4,000,000 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 117 km SSE of Ugashik, Alaska · 50 km NE of this epicentre May 29, 2015
2. 6.5 60 km ENE of Chignik, Alaska · 33 km NW of this epicentre Sep 28, 1941
3. 6.4 61 km ENE of Chignik, Alaska · 41 km NW of this epicentre Jan 1, 1963
4. 6.4 77 km ESE of Chignik, Alaska · 22 km SSW of this epicentre Mar 24, 1972
5. 6.4 104 km SSE of Ugashik, Alaska · 42 km NNE of this epicentre May 20, 1979

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 56.3197, -157.0698. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.1 117 km SSE of Ugashik, Alaska 07:52 UTC
2. 2.2 60 km ENE of Chignik, Alaska 00:08 UTC
3. 2.1 104 km E of Chignik, Alaska 02:21 UTC
4. 2.2 109 km E of Chignik, Alaska 16:25 UTC
5. 3.3 112 km E of Chignik, Alaska 18:21 UTC
6. 1.7 105 km SSE of Ugashik, Alaska 00:59 UTC
7. 1.9 63 km ESE of Chignik, Alaska 12:02 UTC
8. 1.7 84 km ENE of Chignik, Alaska 21:27 UTC
9. 1.6 116 km E of Chignik, Alaska 07:17 UTC
10. 1.8 104 km E of Chignik, Alaska 22:05 UTC
11. 1.7 92 km ENE of Chignik, Alaska 08:07 UTC
12. 1.6 103 km E of Chignik, Alaska 09:39 UTC
13. 2.3 83 km ENE of Chignik, Alaska 04:23 UTC
14. 2.1 99 km E of Chignik, Alaska 06:36 UTC
15. 2.5 86 km ENE of Chignik, Alaska 05:56 UTC

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