94 km NNE of Adak, 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 it was probably too small to be felt, even directly above it. 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 4.8 on 2020-04-27 — about 11 times the energy of this one.

Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:

1. 5.8 76 km ENE of Adak, Alaska · 47 km SSE of this epicentre Aug 7, 2008
2. 5.4 94 km NNE of Adak, Alaska · 17 km WNW of this epicentre Apr 20, 2007
3. 5.3 56 km NNE of Adak, Alaska · 40 km SW of this epicentre Aug 7, 1977
4. 5.1 94 km NE of Adak, Alaska · 30 km SE of this epicentre Jan 8, 1975
5. 5.1 89 km WNW of Atka, Alaska · 36 km E of this epicentre Aug 28, 1976

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 52.5875, -175.8742. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.3 73 km ENE of Adak, Alaska 20:57 UTC
2. 2.6 57 km NNE of Adak, Alaska 05:10 UTC
3. 2.9 90 km NE of Adak, Alaska 14:12 UTC
4. 2.0 89 km W of Atka, Alaska 03:07 UTC
5. 2.0 123 km NW of Atka, Alaska 14:57 UTC
6. 3.0 75 km ENE of Adak, Alaska 08:29 UTC
7. 3.5 85 km WNW of Atka, Alaska 16:11 UTC
8. 2.4 86 km NE of Adak, Alaska 06:01 UTC
9. 2.5 91 km NNE of Adak, Alaska 08:35 UTC
10. 2.1 65 km ENE of Adak, Alaska 12:25 UTC
11. 1.9 56 km NE of Adak, Alaska 09:00 UTC
12. 3.0 73 km ENE of Adak, Alaska 11:53 UTC
13. 2.3 48 km NE of Adak, Alaska 11:08 UTC
14. 2.9 50 km NNE of Adak, Alaska 22:31 UTC
15. 2.5 57 km NE of Adak, Alaska 18:12 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 16:41 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.