159 km S of False Pass, 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 6 km (4 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 5.9 on 2016-10-27 — about 130,000 times the energy of this one.

Before 2016, the USGS record lists 57 earthquakes of M5 or more within 50 km; the five largest:

1. 8.6 The 1946 Unimak Island, Alaska Earthquake · 48 km E of this epicentre Apr 1, 1946
2. 6.6 146 km ESE of Akutan, Alaska · 20 km NW of this epicentre Apr 1, 1946
3. 6.2 Unimak Island region, Alaska · 47 km NNW of this epicentre Oct 14, 1933
4. 6.2 136 km SE of Akutan, Alaska · 34 km W of this epicentre Apr 1, 1946
5. 6.2 136 km S of False Pass, Alaska · 28 km NNW of this epicentre Apr 2, 1946

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 53.4258, -163.5542. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.8 150 km S of False Pass, Alaska 06:59 UTC
2. 4.5 Unimak Island region, Alaska 05:20 UTC
3. 4.3 146 km S of False Pass, Alaska 05:10 UTC
4. 2.5 123 km ESE of Akutan, Alaska 05:03 UTC
5. 2.0 135 km SE of Akutan, Alaska 01:03 UTC
6. 4.5 122 km ESE of Akutan, Alaska 09:56 UTC
7. 3.1 153 km SE of Akutan, Alaska 02:18 UTC
8. 2.8 120 km S of False Pass, Alaska 05:58 UTC
9. 2.7 120 km ESE of Akutan, Alaska 01:28 UTC
10. 2.8 123 km ESE of Akutan, Alaska 19:55 UTC
11. 3.3 122 km ESE of Akutan, Alaska 17:19 UTC
12. 2.5 115 km S of False Pass, Alaska 08:09 UTC
13. 2.2 154 km S of False Pass, Alaska 20:45 UTC
14. 2.4 160 km S of False Pass, Alaska 14:03 UTC
15. 4.4 153 km S of False Pass, Alaska 06:42 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:39 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.