110 km E 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 16 km (10 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 43 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 350,000× the energy of this one
2. Magna, Utah 2020 M 5.7 250,000× the energy of this one
3. Around the size people start to feel M 3.0 22× the energy of this one
4. This earthquake M 2.1 about 43 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 16,000,000 times the energy of this one.

Before 2016, the USGS record lists 16 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 117 km SSE of Ugashik, Alaska · 28 km NNE of this epicentre May 29, 2015
2. 6.4 77 km ESE of Chignik, Alaska · 44 km SW of this epicentre Mar 24, 1972
3. 6.4 104 km SSE of Ugashik, Alaska · 33 km NNW of this epicentre May 20, 1979
4. 6.3 112 km E of Chignik, Alaska · 19 km S of this epicentre Feb 25, 1953
5. 6.1 132 km E of Chignik, Alaska · 28 km SE of this epicentre Sep 13, 1911

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 56.3595, -156.6144. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.5 119 km SSE of Ugashik, Alaska 17:28 UTC
2. 2.5 108 km E of Chignik, Alaska 01:23 UTC
3. 2.8 98 km E of Chignik, Alaska 18:12 UTC
4. 1.9 97 km ENE of Chignik, Alaska 22:41 UTC
5. 2.4 118 km E of Chignik, Alaska 06:51 UTC
6. 2.7 104 km SE of Ugashik, Alaska 01:02 UTC
7. 2.4 93 km ENE of Chignik, Alaska 02:47 UTC
8. 2.2 113 km E of Chignik, Alaska 14:31 UTC
9. 3.6 115 km E of Chignik, Alaska 01:05 UTC
10. 2.8 117 km E of Chignik, Alaska 12:53 UTC
11. 2.7 106 km ENE of Chignik, Alaska 02:39 UTC
12. 2.1 103 km ESE of Chignik, Alaska 01:51 UTC
13. 2.4 140 km ESE of Chignik, Alaska 20:42 UTC
14. 2.4 143 km ESE of Chignik, Alaska 06:11 UTC
15. 2.6 116 km E of Chignik, Alaska 09:34 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:35 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.