122 km ESE of Sand Point, Alaska

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 276 km (171 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 3.8 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.6 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 45× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2× the energy of this one
3. Magna, Utah 2020 M 5.7 1.4× the energy of this one
4. This earthquake M 5.6 about 3.8 kilotons of TNT
5. Around the size people start to feel M 3.0 this one released 7,900× more

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 7.8 on 2020-07-22 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 10 earthquakes of M5 or more within 50 km; the five largest:

1. 6.6 104 km SSE of Perryville, Alaska · 34 km NNE of this epicentre Nov 11, 1938
2. 6.6 85 km SE of Sand Point, Alaska · 47 km W of this epicentre Oct 9, 1985
3. 6.5 94 km ESE of Sand Point, Alaska · 29 km NW of this epicentre Feb 14, 1983
4. 5.9 113 km SE of Sand Point, Alaska · 27 km WSW of this epicentre Jun 7, 1917
5. 5.9 99 km SE of Sand Point, Alaska · 44 km WSW 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 54.7461, -158.8750. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.7 132 km SSE of Perryville, Alaska 00:32 UTC
2. 2.6 101 km SSE of Perryville, Alaska 00:17 UTC
3. 2.2 96 km SSE of Perryville, Alaska 00:06 UTC
4. 2.2 120 km ESE of Sand Point, Alaska 23:48 UTC
5. 2.1 92 km SSE of Perryville, Alaska 22:04 UTC
6. 2.2 123 km SSE of Perryville, Alaska 19:52 UTC
7. 4.0 94 km SSE of Perryville, Alaska 19:37 UTC
8. 2.5 138 km SSE of Perryville, Alaska 16:52 UTC
9. 2.2 119 km SSE of Perryville, Alaska 15:49 UTC
10. 4.1 84 km S of Perryville, Alaska 15:31 UTC
11. 2.5 127 km SSE of Perryville, Alaska 15:17 UTC
12. 2.2 123 km SSE of Perryville, Alaska 14:31 UTC
13. 4.5 120 km SSE of Perryville, Alaska 13:33 UTC
14. 2.6 96 km S of Perryville, Alaska 13:11 UTC
15. 4.4 127 km SSE of Perryville, Alaska 12:33 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 00:48 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.