116 km SE 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 9 km (6 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 5.9 on 2021-07-29 — about 500,000 times the energy of this one.

Before 2016, the USGS record lists 12 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 113 km ESE of Chignik, Alaska · 21 km NNE of this epicentre May 4, 1923
2. 7.0 164 km SE of Chignik, Alaska · 49 km SE of this epicentre Sep 4, 1989
3. 6.9 143 km ESE of Chignik, Alaska · 43 km ENE of this epicentre Feb 13, 1951
4. 6.7 121 km SE of Chignik, Alaska · 28 km SSW of this epicentre Feb 13, 1979
5. 6.6 128 km SE of Chignik, Alaska · 13 km ESE of this epicentre Jul 28, 1934

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 55.6670, -156.9188. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.6 82 km ESE of Chignik, Alaska 08:49 UTC
2. 2.4 134 km ESE of Chignik, Alaska 17:42 UTC
3. 2.6 126 km SE of Chignik, Alaska 21:59 UTC
4. 2.0 88 km ESE of Chignik, Alaska 02:24 UTC
5. 2.3 94 km ESE of Chignik, Alaska 22:12 UTC
6. 2.8 129 km SE of Chignik, Alaska 23:26 UTC
7. 2.2 95 km SE of Chignik, Alaska 10:34 UTC
8. 2.5 103 km ESE of Chignik, Alaska 15:41 UTC
9. 2.8 131 km SE of Chignik, Alaska 02:45 UTC
10. 4.4 100 km SE of Chignik, Alaska 14:37 UTC
11. 2.9 92 km ESE of Chignik, Alaska 12:52 UTC
12. 2.2 111 km ESE of Chignik, Alaska 09:09 UTC
13. 2.4 132 km ESE of Chignik, Alaska 04:31 UTC
14. 2.8 129 km ESE of Chignik, Alaska 17:27 UTC
15. 2.3 73 km ESE of Chignik, Alaska 15:24 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:09 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.