124 km SSW of Atka, 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 6.3 on 2019-11-24 — about 500,000 times the energy of this one.

Before 2016, the USGS record lists 129 earthquakes of M5 or more within 50 km; the five largest:

1. 8.0 1986 Atka, Alaska Earthquake · 40 km NNE of this epicentre May 7, 1986
2. 7.0 153 km SE of Adak, Alaska · 39 km SSW of this epicentre Jan 17, 1903
3. 7.0 101 km SW of Atka, Alaska · 43 km NNW of this epicentre Aug 30, 2013
4. 6.9 100 km ESE of Adak, Alaska · 43 km NNW of this epicentre Oct 13, 1926
5. 6.8 99 km SW of Atka, Alaska · 38 km NNW of this epicentre Mar 19, 1957

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 51.1856, -174.9857. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 4.0 114 km SE of Adak, Alaska 12:45 UTC
2. 3.8 106 km SE of Adak, Alaska 05:43 UTC
3. 4.1 105 km SE of Adak, Alaska 05:19 UTC
4. 2.7 107 km SE of Adak, Alaska 23:32 UTC
5. 3.6 116 km SE of Adak, Alaska 23:00 UTC
6. 3.3 128 km SE of Adak, Alaska 21:48 UTC
7. 4.7 120 km SE of Adak, Alaska 19:28 UTC
8. 3.0 114 km SE of Adak, Alaska 17:33 UTC
9. 4.6 119 km SE of Adak, Alaska 17:03 UTC
10. 2.7 107 km ESE of Adak, Alaska 16:47 UTC
11. 3.1 109 km SE of Adak, Alaska 16:32 UTC
12. 2.8 108 km SE of Adak, Alaska 16:30 UTC
13. 2.9 110 km SE of Adak, Alaska 15:48 UTC
14. 3.2 113 km SE of Adak, Alaska 15:44 UTC
15. 2.6 109 km SE of Adak, Alaska 15:28 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:00 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.