126 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 19 km (12 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 680 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 22,000× the energy of this one
2. Magna, Utah 2020 M 5.7 16,000× the energy of this one
3. Around the size people start to feel M 3.0 1.4× the energy of this one
4. This earthquake M 2.9 about 680 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 7.6 on 2020-10-19 — about 11,000,000 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

1. 5.9 99 km SE of Sand Point, Alaska · 47 km NNE of this epicentre Oct 20, 1929
2. 5.9 131 km S of Sand Point, Alaska · 37 km WSW of this epicentre Dec 3, 1933

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 54.2630, -159.8610. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.3 103 km SSE of Sand Point, Alaska 21:56 UTC
2. 2.4 100 km SSE of Sand Point, Alaska 21:17 UTC
3. 2.4 127 km SSE of Sand Point, Alaska 16:22 UTC
4. 2.9 94 km SSE of Sand Point, Alaska 15:46 UTC
5. 2.4 96 km SSE of Sand Point, Alaska 09:16 UTC
6. 2.5 105 km SSE of Sand Point, Alaska 06:40 UTC
7. 2.9 116 km SSE of Sand Point, Alaska 17:53 UTC
8. 2.4 113 km SSE of Sand Point, Alaska 16:32 UTC
9. 3.0 86 km S of Sand Point, Alaska 16:06 UTC
10. 2.8 106 km SSE of Sand Point, Alaska 14:50 UTC
11. 2.7 114 km SSE of Sand Point, Alaska 14:26 UTC
12. 2.4 104 km SSE of Sand Point, Alaska 12:47 UTC
13. 3.2 90 km SSE of Sand Point, Alaska 23:57 UTC
14. 2.6 109 km S of Sand Point, Alaska 04:06 UTC
15. 2.3 124 km SSE of Sand Point, Alaska 03:29 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 22:42 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.