200 km S of Adak, 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 20 km (12 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 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
3. Around the size people start to feel M 3.0 5.6× the energy of this one
4. This earthquake M 2.5 about 170 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 4.7 on 2016-11-29 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

1. 6.3 204 km SSE of Adak, Alaska · 44 km ENE of this epicentre Feb 22, 1958
2. 5.7 Andreanof Islands, Aleutian Islands, Alaska · 15 km WNW of this epicentre Feb 5, 1981
3. 5.5 187 km SSE of Adak, Alaska · 14 km N of this epicentre Apr 15, 1992
4. 5.4 201 km SSE of Adak, Alaska · 20 km E of this epicentre Feb 26, 2015
5. 5.3 185 km S of Adak, Alaska · 15 km N of this epicentre Jun 26, 2006

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 50.1065, -176.0785. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 4.2 167 km S of Adak, Alaska 12:30 UTC
2. 2.6 168 km S of Adak, Alaska 04:26 UTC
3. 2.7 213 km SSE of Adak, Alaska 16:34 UTC
4. 2.5 173 km SSE of Adak, Alaska 01:41 UTC
5. 2.9 169 km S of Adak, Alaska 10:29 UTC
6. 2.5 188 km SSE of Adak, Alaska 14:09 UTC
7. 2.9 193 km SSE of Adak, Alaska 09:44 UTC
8. 2.0 171 km S of Adak, Alaska 19:42 UTC
9. 2.4 185 km S of Adak, Alaska 08:24 UTC
10. 2.7 159 km SSE of Adak, Alaska 04:17 UTC
11. 2.9 182 km S of Adak, Alaska 16:34 UTC
12. 2.1 154 km S of Adak, Alaska 05:16 UTC
13. 3.4 162 km S of Adak, Alaska 11:03 UTC
14. 3.0 191 km SSE of Adak, Alaska 04:28 UTC
15. 3.6 184 km S of Adak, Alaska 02:08 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 08:14 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.