100 km SE 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 75 km (47 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 5.4 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.7 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 32,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,400× the energy of this one
3. Magna, Utah 2020 M 5.7 1,000× the energy of this one
4. This earthquake M 3.7 about 5.4 tons of TNT
5. Around the size people start to feel M 3.0 this one released 11× 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 113 km ESE of Chignik, Alaska · 20 km ENE of this epicentre May 4, 1923
2. 6.9 143 km ESE of Chignik, Alaska · 50 km E of this epicentre Feb 13, 1951
3. 6.7 121 km SE of Chignik, Alaska · 38 km S of this epicentre Feb 13, 1979
4. 6.6 128 km SE of Chignik, Alaska · 28 km SE of this epicentre Jul 28, 1934
5. 6.4 77 km ESE of Chignik, Alaska · 39 km N of this epicentre Mar 24, 1972

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 55.7893, -157.0728. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.3 107 km SSE of Chignik, Alaska 12:54 UTC
2. 3.6 137 km SE of Chignik, Alaska 12:32 UTC
3. 3.5 126 km SE of Chignik, Alaska 12:23 UTC
4. 2.3 110 km ESE of Chignik, Alaska 12:14 UTC
5. 3.2 137 km SE of Chignik, Alaska 11:56 UTC
6. 2.1 88 km SE of Chignik, Alaska 11:25 UTC
7. 2.5 95 km SE of Chignik, Alaska 10:29 UTC
8. 3.2 135 km SE of Chignik, Alaska 10:22 UTC
9. 3.3 113 km SE of Chignik, Alaska 09:38 UTC
10. 3.3 101 km SE of Chignik, Alaska 09:30 UTC
11. 2.8 124 km SE of Chignik, Alaska 09:14 UTC
12. 3.5 118 km SSE of Chignik, Alaska 08:38 UTC
13. 3.3 122 km SE of Chignik, Alaska 08:24 UTC
14. 3.0 106 km SE of Chignik, Alaska 08:12 UTC
15. 4.1 135 km SE of Chignik, Alaska 08:08 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:48 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.