169 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 5 km (3 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 340 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.7 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 45,000× the energy of this one
2. Magna, Utah 2020 M 5.7 32,000× the energy of this one
3. Around the size people start to feel M 3.0 2.8× the energy of this one
4. This earthquake M 2.7 about 340 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 5.5 on 2021-07-30 — about 16,000 times the energy of this one.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 164 km SE of Chignik, Alaska · 23 km NNE of this epicentre Sep 4, 1989
2. 6.7 121 km SE of Chignik, Alaska · 48 km NW of this epicentre Feb 13, 1979
3. 6.2 189 km SE of Chignik, Alaska · 23 km SSE of this epicentre Mar 18, 1945
4. 6.0 168 km SE of Chignik, Alaska · 15 km NE of this epicentre Nov 16, 1938
5. 5.6 171 km SE of Chignik, Alaska · 2 km ESE of this epicentre Jun 22, 1970

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 55.1504, -156.6239. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.4 156 km SSE of Chignik, Alaska 23:48 UTC
2. 2.5 138 km SE of Chignik, Alaska 12:47 UTC
3. 2.4 south of Alaska 04:20 UTC
4. 2.7 129 km SE of Chignik, Alaska 03:57 UTC
5. 2.7 197 km SE of Chignik, Alaska 09:52 UTC
6. 3.3 144 km SSE of Chignik, Alaska 12:19 UTC
7. 2.6 190 km SE of Chignik, Alaska 11:57 UTC
8. 2.3 177 km SE of Chignik, Alaska 08:58 UTC
9. 3.4 163 km SE of Chignik, Alaska 05:46 UTC
10. 3.0 154 km SE of Chignik, Alaska 17:41 UTC
11. 2.4 162 km SE of Chignik, Alaska 12:56 UTC
12. 3.3 193 km SE of Perryville, Alaska 17:33 UTC
13. 3.0 175 km SE of Perryville, Alaska 17:01 UTC
14. 2.3 161 km SE of Chignik, Alaska 13:02 UTC
15. 2.9 189 km SE of Perryville, Alaska 12:59 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 08:12 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.