164 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 1 km (1 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 30 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.0 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 500,000× the energy of this one
2. Magna, Utah 2020 M 5.7 350,000× the energy of this one
3. Around the size people start to feel M 3.0 32× the energy of this one
4. This earthquake M 2.0 about 30 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 4.8 on 2021-07-29 — about 16,000 times the energy of this one.

Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:

1. 6.9 143 km ESE of Chignik, Alaska · 21 km WNW of this epicentre Feb 13, 1951
2. 6.9 171 km SW of Akhiok, Alaska · 7 km ESE of this epicentre Feb 6, 1964
3. 6.2 148 km SSW of Akhiok, Alaska · 47 km E of this epicentre Nov 10, 1944
4. 6.1 118 km ESE of Chignik, Alaska · 46 km WNW of this epicentre Mar 16, 1940
5. 5.9 169 km ESE of Chignik, Alaska · 15 km S of this epicentre Feb 6, 1964

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 55.7455, -155.9526. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.9 165 km SE of Chignik, Alaska 13:56 UTC
2. 2.6 177 km SSW of Akhiok, Alaska 17:37 UTC
3. 1.8 157 km SSW of Akhiok, Alaska 19:45 UTC
4. 3.0 169 km ESE of Chignik, Alaska 10:05 UTC
5. 1.6 south of Alaska 09:35 UTC
6. 2.8 190 km SSW of Akhiok, Alaska 06:38 UTC
7. 3.0 158 km SE of Chignik, Alaska 19:15 UTC
8. 1.9 144 km ESE of Chignik, Alaska 02:51 UTC
9. 2.4 170 km SE of Chignik, Alaska 21:22 UTC
10. 2.6 166 km ESE of Chignik, Alaska 01:41 UTC
11. 2.4 162 km SW of Akhiok, Alaska 11:42 UTC
12. 2.5 152 km SW of Akhiok, Alaska 01:26 UTC
13. 3.3 150 km ESE of Chignik, Alaska 08:44 UTC
14. 2.0 154 km ESE of Chignik, Alaska 02:09 UTC
15. 2.6 182 km SE of Chignik, Alaska 06:44 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:14 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.