148 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 9 km (6 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 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
3. Around the size people start to feel M 3.0 2× the energy of this one
4. This earthquake M 2.8 about 480 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 5.0 on 2016-06-18 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 51 earthquakes of M5 or more within 50 km; the five largest:

1. 8.6 The 1946 Unimak Island, Alaska Earthquake · 21 km E of this epicentre Apr 1, 1946
2. 6.6 146 km ESE of Akutan, Alaska · 43 km W of this epicentre Apr 1, 1946
3. 6.2 136 km S of False Pass, Alaska · 43 km WNW of this epicentre Apr 2, 1946
4. 6.2 172 km SSE of False Pass, Alaska · 28 km SE of this epicentre Apr 2, 1946
5. 6.2 184 km SE of Akutan, Alaska · 43 km SSW of this epicentre Apr 6, 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 53.5276, -163.1379. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.6 147 km S of False Pass, Alaska 12:54 UTC
2. 2.4 147 km S of False Pass, Alaska 12:51 UTC
3. 2.8 133 km S of False Pass, Alaska 12:48 UTC
4. 5.1 134 km S of False Pass, Alaska 12:44 UTC
5. 2.6 139 km S of False Pass, Alaska 12:43 UTC
6. 3.4 152 km S of False Pass, Alaska 12:30 UTC
7. 3.5 151 km S of False Pass, Alaska 12:29 UTC
8. 2.6 144 km S of False Pass, Alaska 12:23 UTC
9. 2.6 162 km S of False Pass, Alaska 12:19 UTC
10. 2.5 147 km S of False Pass, Alaska 12:16 UTC
11. 2.7 146 km S of False Pass, Alaska 12:13 UTC
12. 2.6 144 km S of False Pass, Alaska 12:10 UTC
13. 3.6 156 km S of False Pass, Alaska 12:09 UTC
14. 3.5 154 km S of False Pass, Alaska 12:08 UTC
15. 3.7 158 km S of False Pass, Alaska 12:04 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 03:56 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.