187 km WSW of Adak, Alaska

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

At this magnitude and depth it was probably too small to be felt, even directly above it. 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 6.1 on 2021-09-24 — about 1,000,000 times the energy of this one.

Before 2016, the USGS record lists 206 earthquakes of M5 or more within 50 km; the five largest:

1. 7.2 162 km WSW of Adak, Alaska · 25 km ENE of this epicentre Mar 16, 1957
2. 7.2 207 km WSW of Adak, Alaska · 21 km W of this epicentre Dec 19, 2007
3. 7.0 148 km WSW of Adak, Alaska · 42 km E of this epicentre Mar 11, 1957
4. 6.9 203 km WSW of Adak, Alaska · 18 km W of this epicentre Mar 31, 1913
5. 6.9 231 km WSW of Adak, Alaska · 45 km W of this epicentre May 14, 1969

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 51.3367, -179.2028. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 181 km W of Adak, Alaska 00:35 UTC
2. 2.4 152 km WSW of Adak, Alaska 20:01 UTC
3. 2.2 213 km WSW of Adak, Alaska 13:21 UTC
4. 2.0 153 km W of Adak, Alaska 06:08 UTC
5. 2.1 174 km W of Adak, Alaska 22:28 UTC
6. 1.6 145 km WSW of Adak, Alaska 10:21 UTC
7. 2.7 169 km W of Adak, Alaska 06:04 UTC
8. 1.7 159 km WSW of Adak, Alaska 07:01 UTC
9. 2.6 219 km WSW of Adak, Alaska 07:45 UTC
10. 2.1 171 km WSW of Adak, Alaska 23:16 UTC
11. 2.0 177 km WSW of Adak, Alaska 05:37 UTC
12. 1.8 176 km WSW of Adak, Alaska 15:18 UTC
13. 1.8 187 km WSW of Adak, Alaska 14:15 UTC
14. 2.5 170 km W of Adak, Alaska 04:11 UTC
15. 2.7 186 km W of Adak, Alaska 12:17 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:58 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.