152 km S of False Pass, 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 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
3. Around the size people start to feel M 3.0 11× the energy of this one
4. This earthquake M 2.3 about 85 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 250,000 times the energy of this one.

Before 2016, the USGS record lists 59 earthquakes of M5 or more within 50 km; the five largest:

1. 8.6 The 1946 Unimak Island, Alaska Earthquake · 44 km E of this epicentre Apr 1, 1946
2. 6.6 146 km ESE of Akutan, Alaska · 20 km WNW of this epicentre Apr 1, 1946
3. 6.2 Unimak Island region, Alaska · 45 km NW of this epicentre Oct 14, 1933
4. 6.2 136 km SE of Akutan, Alaska · 38 km W of this epicentre Apr 1, 1946
5. 6.2 136 km S of False Pass, Alaska · 25 km NW 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 53.4818, -163.4995. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.5 156 km S of False Pass, Alaska 09:25 UTC
2. 2.8 156 km S of False Pass, Alaska 13:25 UTC
3. 2.8 139 km S of False Pass, Alaska 19:49 UTC
4. 2.3 111 km S of False Pass, Alaska 11:47 UTC
5. 3.9 106 km S of False Pass, Alaska 22:57 UTC
6. 3.9 167 km S of False Pass, Alaska 23:27 UTC
7. 2.4 166 km S of False Pass, Alaska 03:50 UTC
8. 2.9 144 km S of False Pass, Alaska 02:14 UTC
9. 2.9 129 km ESE of Akutan, Alaska 01:34 UTC
10. 2.6 106 km S of False Pass, Alaska 19:32 UTC
11. 3.1 150 km S of False Pass, Alaska 01:42 UTC
12. 2.2 120 km SSW of False Pass, Alaska 09:29 UTC
13. 2.8 166 km ESE of Akutan, Alaska 10:18 UTC
14. 3.1 129 km SSW of False Pass, Alaska 13:18 UTC
15. 3.7 166 km S of False Pass, Alaska 13:40 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 23:08 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.