124 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 3 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 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
3. Around the size people start to feel M 3.0 2× the energy of this one
4. This earthquake M 2.8 about 480 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 5.9 on 2021-07-29 — about 45,000 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 113 km ESE of Chignik, Alaska · 43 km NNE of this epicentre May 4, 1923
2. 7.0 164 km SE of Chignik, Alaska · 43 km ESE of this epicentre Sep 4, 1989
3. 6.9 105 km ESE of Perryville, Alaska · 44 km W of this epicentre Nov 17, 1938
4. 6.7 121 km SE of Chignik, Alaska · 8 km WSW of this epicentre Feb 13, 1979
5. 6.6 128 km SE of Chignik, Alaska · 26 km NE of this epicentre Jul 28, 1934

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 55.4822, -157.0478. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.5 125 km SE of Chignik, Alaska 16:34 UTC
2. 3.0 152 km SE of Chignik, Alaska 16:28 UTC
3. 2.6 151 km SE of Chignik, Alaska 16:26 UTC
4. 2.6 157 km SSE of Chignik, Alaska 16:17 UTC
5. 5.3 155 km SE of Chignik, Alaska 16:09 UTC
6. 2.7 139 km SE of Perryville, Alaska 15:27 UTC
7. 2.5 144 km SSE of Chignik, Alaska 15:19 UTC
8. 3.6 150 km SE of Chignik, Alaska 15:13 UTC
9. 2.6 133 km SE of Chignik, Alaska 15:12 UTC
10. 2.9 129 km SE of Chignik, Alaska 15:06 UTC
11. 2.7 143 km SE of Chignik, Alaska 15:02 UTC
12. 3.0 Alaska Peninsula 14:48 UTC
13. 2.8 149 km SE of Perryville, Alaska 14:45 UTC
14. 2.8 141 km SE of Chignik, Alaska 14:42 UTC
15. 2.4 141 km SSE of Chignik, Alaska 14:17 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:22 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.