220 km SSE 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 35 km (22 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 5.3 on 2020-12-16 — about 2,800 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

1. 5.7 208 km SSE of Sand Point, Alaska · 12 km N of this epicentre May 17, 1964
2. 5.5 241 km S of Sand Point, Alaska · 47 km SW of this epicentre May 23, 1969
3. 5.5 233 km S of Sand Point, Alaska · 22 km SW of this epicentre May 20, 1972
4. 5.0 188 km SSE of Sand Point, Alaska · 32 km NNW of this epicentre Oct 16, 2001

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 53.4050, -159.7585. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.1 187 km S of Sand Point, Alaska 10:36 UTC
2. 3.3 201 km S of Sand Point, Alaska 08:43 UTC
3. 3.3 194 km S of Sand Point, Alaska 19:15 UTC
4. 4.2 202 km S of Sand Point, Alaska 16:48 UTC
5. 2.8 207 km SSE of Sand Point, Alaska 05:49 UTC
6. 3.0 241 km S of Sand Point, Alaska 23:28 UTC
7. 2.5 208 km S of Sand Point, Alaska 02:39 UTC
8. 3.4 209 km S of Sand Point, Alaska 00:38 UTC
9. 3.7 224 km S of Sand Point, Alaska 14:44 UTC
10. 2.6 209 km SSE of Sand Point, Alaska 16:44 UTC
11. 3.0 198 km S of Sand Point, Alaska 18:17 UTC
12. 2.0 217 km S of Sand Point, Alaska 21:32 UTC
13. 2.8 215 km S of Sand Point, Alaska 00:30 UTC
14. 2.4 220 km S of Sand Point, Alaska 11:52 UTC
15. 3.3 224 km SSE of Sand Point, Alaska 14:24 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 23:02 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.