125 km SSE of Perryville, Alaska

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 103 km (64 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 21 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.1 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 7,900× the energy of this one
2. Mineral, Virginia 2011 M 5.8 350× the energy of this one
3. Magna, Utah 2020 M 5.7 250× the energy of this one
4. This earthquake M 4.1 about 21 tons of TNT
5. Around the size people start to feel M 3.0 this one released 45× 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 350,000 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

1. 8.2 1938 Semidi Islands, Alaska Earthquake · 41 km NNE of this epicentre Nov 10, 1938
2. 6.6 104 km SSE of Perryville, Alaska · 21 km NNW of this epicentre Nov 11, 1938
3. 6.5 94 km ESE of Sand Point, Alaska · 46 km WNW of this epicentre Feb 14, 1983
4. 6.2 143 km SE of Perryville, Alaska · 48 km E of this epicentre Mar 25, 1927
5. 5.9 90 km ESE of Sand Point, Alaska · 50 km WNW of this epicentre Feb 14, 1983

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 54.8522, -158.4865. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 130 km SSE of Perryville, Alaska 11:50 UTC
2. 2.2 102 km SSE of Perryville, Alaska 13:37 UTC
3. 3.0 121 km ESE of Sand Point, Alaska 11:38 UTC
4. 1.9 132 km SSE of Perryville, Alaska 08:39 UTC
5. 2.3 111 km SSE of Perryville, Alaska 06:09 UTC
6. 2.0 85 km SSE of Perryville, Alaska 03:57 UTC
7. 2.1 108 km SSE of Perryville, Alaska 22:48 UTC
8. 2.0 106 km SSE of Perryville, Alaska 22:29 UTC
9. 2.5 113 km SSE of Perryville, Alaska 18:26 UTC
10. 1.9 108 km SSE of Perryville, Alaska 23:41 UTC
11. 2.6 112 km ESE of Sand Point, Alaska 18:36 UTC
12. 1.8 90 km SSE of Perryville, Alaska 10:50 UTC
13. 2.3 124 km SSE of Perryville, Alaska 00:34 UTC
14. 1.9 98 km SSE of Perryville, Alaska 22:16 UTC
15. 3.1 113 km ESE of Sand Point, Alaska 20:36 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 13:06 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.