71 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 4 km (2 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 5.7 on 2021-07-29 — about 250,000 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

1. 7.0 113 km ESE of Chignik, Alaska · 46 km E of this epicentre May 4, 1923
2. 6.4 77 km ESE of Chignik, Alaska · 33 km NE of this epicentre Mar 24, 1972
3. 5.5 51 km SSE of Chignik, Alaska · 44 km W of this epicentre Feb 24, 1972
4. 5.1 116 km SE of Chignik, Alaska · 48 km SSE of this epicentre Feb 12, 1979
5. 5.1 85 km ESE of Chignik, Alaska · 33 km NE of this epicentre Jan 7, 2006

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 55.8947, -157.5070. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.1 69 km ESE of Chignik, Alaska 04:43 UTC
2. 1.8 90 km SE of Chignik, Alaska 14:53 UTC
3. 2.4 102 km SE of Chignik, Alaska 12:09 UTC
4. 1.9 63 km SE of Chignik, Alaska 03:27 UTC
5. 2.7 81 km SE of Chignik, Alaska 10:20 UTC
6. 1.9 71 km SSE of Chignik, Alaska 20:28 UTC
7. 2.1 83 km SE of Chignik, Alaska 11:36 UTC
8. 2.1 Alaska Peninsula 14:36 UTC
9. 2.5 88 km SE of Chignik, Alaska 14:07 UTC
10. 3.2 30 km ESE of Chignik, Alaska 06:44 UTC
11. 2.1 59 km SSE of Chignik, Alaska 15:32 UTC
12. 2.5 74 km E of Chignik, Alaska 19:17 UTC
13. 2.2 60 km ESE of Chignik, Alaska 07:56 UTC
14. 2.4 72 km ESE of Chignik, Alaska 07:42 UTC
15. 1.9 63 km ESE of Chignik, Alaska 21:03 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 01:27 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.