222 km S of Adak, Alaska

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 12 km (7 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 43 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 350,000× the energy of this one
2. Magna, Utah 2020 M 5.7 250,000× the energy of this one
3. Around the size people start to feel M 3.0 22× the energy of this one
4. This earthquake M 2.1 about 43 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 4.3 on 2019-06-30 — 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. 6.2 204 km S of Adak, Alaska · 21 km NNE of this epicentre Dec 9, 1918
2. 6.1 198 km S of Adak, Alaska · 24 km N of this epicentre May 22, 1957
3. 6.1 189 km S of Adak, Alaska · 35 km NNW of this epicentre Jul 3, 1960
4. 5.8 176 km S of Adak, Alaska · 46 km N of this epicentre Apr 10, 1957
5. 5.7 193 km S of Adak, Alaska · 29 km N of this epicentre Sep 26, 1963

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 49.8801, -176.9188. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.1 222 km S of Adak, Alaska 20:58 UTC
2. 2.6 200 km S of Adak, Alaska 09:24 UTC
3. 3.2 176 km S of Adak, Alaska 16:45 UTC
4. 2.9 191 km S of Adak, Alaska 19:37 UTC
5. 2.4 185 km S of Adak, Alaska 08:24 UTC
6. 2.5 182 km S of Adak, Alaska 01:43 UTC
7. 2.3 191 km SSW of Adak, Alaska 10:21 UTC
8. 2.2 261 km S of Adak, Alaska 14:57 UTC
9. 2.8 189 km S of Adak, Alaska 05:01 UTC
10. 3.4 208 km S of Adak, Alaska 01:22 UTC
11. 2.8 174 km S of Adak, Alaska 06:12 UTC
12. 2.2 195 km SSW of Adak, Alaska 02:08 UTC
13. 2.0 187 km SSW of Adak, Alaska 08:47 UTC
14. 2.7 191 km S of Adak, Alaska 18:21 UTC
15. 2.4 205 km S of Adak, Alaska 06:22 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 02:42 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.