142 km SE of Sand Point, 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 25 km (16 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 950 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.0 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 350,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 16,000× the energy of this one
3. Magna, Utah 2020 M 5.7 11,000× the energy of this one
4. This earthquake M 3.0 about 950 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 5.6 on 2020-07-22 — about 7,900 times the energy of this one.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

1. 6.5 183 km SSE of Perryville, Alaska · 49 km ESE of this epicentre Jul 1, 1967
2. 5.9 113 km SE of Sand Point, Alaska · 31 km WNW of this epicentre Jun 7, 1917
3. 5.9 99 km SE of Sand Point, Alaska · 49 km WNW of this epicentre Oct 20, 1929

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 54.5107, -158.8074. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.6 124 km SSE of Perryville, Alaska 20:17 UTC
2. 2.5 116 km ESE of Sand Point, Alaska 00:01 UTC
3. 2.0 123 km SSE of Perryville, Alaska 04:47 UTC
4. 2.5 117 km S of Perryville, Alaska 19:33 UTC
5. 3.3 160 km SE of Sand Point, Alaska 10:49 UTC
6. 2.3 128 km SSE of Perryville, Alaska 13:17 UTC
7. 2.9 142 km SSE of Perryville, Alaska 06:34 UTC
8. 4.1 120 km SE of Sand Point, Alaska 18:59 UTC
9. 2.2 114 km SE of Sand Point, Alaska 15:40 UTC
10. 2.5 130 km SSE of Perryville, Alaska 09:11 UTC
11. 2.8 101 km SE of Sand Point, Alaska 22:03 UTC
12. 2.8 159 km SE of Sand Point, Alaska 04:17 UTC
13. 2.2 149 km SE of Sand Point, Alaska 03:59 UTC
14. 3.0 157 km SE of Sand Point, Alaska 18:01 UTC
15. 2.6 162 km SE of Sand Point, Alaska 01:30 UTC

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