103 km E of Chignik, Alaska

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 63 km (39 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 2.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 63,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2,800× the energy of this one
3. Magna, Utah 2020 M 5.7 2,000× the energy of this one
4. This earthquake M 3.5 about 2.7 tons of TNT
5. Around the size people start to feel M 3.0 this one released 5.6× 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 6.9 on 2021-10-11 — about 130,000 times the energy of this one.

Before 2016, the USGS record lists 17 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 117 km SSE of Ugashik, Alaska · 26 km NE of this epicentre May 29, 2015
2. 6.5 60 km ENE of Chignik, Alaska · 46 km W of this epicentre Sep 28, 1941
3. 6.4 77 km ESE of Chignik, Alaska · 44 km SW of this epicentre Mar 24, 1972
4. 6.4 104 km SSE of Ugashik, Alaska · 23 km N of this epicentre May 20, 1979
5. 6.3 112 km E of Chignik, Alaska · 30 km SSE of this epicentre Feb 25, 1953

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 56.4451, -156.7501. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.0 106 km SE of Ugashik, Alaska 10:32 UTC
2. 2.4 93 km ESE of Chignik, Alaska 17:53 UTC
3. 3.9 106 km E of Chignik, Alaska 14:17 UTC
4. 2.6 117 km E of Chignik, Alaska 12:51 UTC
5. 2.9 118 km E of Chignik, Alaska 14:35 UTC
6. 2.0 117 km E of Chignik, Alaska 05:31 UTC
7. 2.4 118 km E of Chignik, Alaska 03:52 UTC
8. 2.8 117 km E of Chignik, Alaska 03:49 UTC
9. 5.4 119 km E of Chignik, Alaska 03:33 UTC
10. 1.7 94 km SE of Ugashik, Alaska 20:32 UTC
11. 2.0 100 km E of Chignik, Alaska 19:10 UTC
12. 2.0 117 km E of Chignik, Alaska 10:06 UTC
13. 2.3 124 km E of Chignik, Alaska 06:48 UTC
14. 2.0 Alaska Peninsula 14:47 UTC
15. 3.0 94 km ESE of Chignik, Alaska 10:04 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 20:52 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.