60 km NE of Chignik, Alaska

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 36 km (22 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 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 11,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 500× the energy of this one
3. Magna, Utah 2020 M 5.7 350× the energy of this one
4. This earthquake M 4.0 about 15 tons of TNT
5. Around the size people start to feel M 3.0 this one released 32× more

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 6.2 on 2016-04-02 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

1. 6.5 60 km ENE of Chignik, Alaska · 15 km SSE of this epicentre Sep 28, 1941
2. 6.4 61 km ENE of Chignik, Alaska · 7 km SE of this epicentre Jan 1, 1963
3. 5.7 71 km ENE of Chignik, Alaska · 21 km ESE of this epicentre Feb 7, 1967
4. 5.6 75 km ENE of Chignik, Alaska · 21 km ESE of this epicentre Sep 14, 1964
5. 5.5 33 km NE of Chignik, Alaska · 30 km WSW of this epicentre Dec 22, 2000

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 56.6184, -157.6250. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.8 68 km SSE of Ugashik, Alaska 05:41 UTC
2. 2.3 52 km E of Port Heiden, Alaska 07:38 UTC
3. 2.1 84 km SSE of Ugashik, Alaska 17:15 UTC
4. 1.8 65 km ENE of Chignik, Alaska 16:39 UTC
5. 1.8 54 km E of Port Heiden, Alaska 06:05 UTC
6. 1.7 70 km E of Chignik, Alaska 07:03 UTC
7. 1.9 51 km E of Port Heiden, Alaska 03:12 UTC
8. 2.1 50 km E of Port Heiden, Alaska 08:09 UTC
9. 2.1 56 km E of Port Heiden, Alaska 07:19 UTC
10. 2.1 54 km SSW of Ugashik, Alaska 08:15 UTC
11. 1.6 39 km E of Port Heiden, Alaska 20:46 UTC
12. 2.1 44 km E of Port Heiden, Alaska 14:27 UTC
13. 2.6 52 km E of Port Heiden, Alaska 13:47 UTC
14. 1.9 62 km SSE of Ugashik, Alaska 22:30 UTC
15. 1.8 50 km ENE of Chignik, Alaska 21:57 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:04 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.