67 km WSW of Adak, 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 3 km (2 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 5.4 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.7 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 32,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,400× the energy of this one
3. Magna, Utah 2020 M 5.7 1,000× the energy of this one
4. This earthquake M 3.7 about 5.4 tons of TNT
5. Around the size people start to feel M 3.0 this one released 11× 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 6.5 on 2018-08-15 — about 16,000 times the energy of this one.

Before 2016, the USGS record lists 97 earthquakes of M5 or more within 50 km; the five largest:

1. 7.9 77 km WSW of Adak, Alaska · 12 km SSW of this epicentre Jun 10, 1996
2. 7.3 88 km WSW of Adak, Alaska · 25 km SW of this epicentre Jul 7, 1929
3. 7.1 60 km SW of Adak, Alaska · 29 km SE of this epicentre Mar 12, 1957
4. 7.0 114 km WSW of Adak, Alaska · 48 km WSW of this epicentre Jul 5, 1929
5. 7.0 69 km SW of Adak, Alaska · 33 km SSE of this epicentre May 2, 1971

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 51.6591, -177.5413. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.1 91 km W of Adak, Alaska 12:34 UTC
2. 1.5 Andreanof Islands, Aleutian Islands, Alaska 11:56 UTC
3. 1.5 91 km W of Adak, Alaska 11:28 UTC
4. 2.0 90 km W of Adak, Alaska 10:15 UTC
5. 2.6 Andreanof Islands, Aleutian Islands, Alaska 10:11 UTC
6. 2.4 90 km W of Adak, Alaska 10:09 UTC
7. 1.7 89 km W of Adak, Alaska 10:02 UTC
8. 2.1 90 km W of Adak, Alaska 09:03 UTC
9. 2.2 91 km W of Adak, Alaska 08:46 UTC
10. 1.6 Andreanof Islands, Aleutian Islands, Alaska 08:45 UTC
11. 2.8 89 km W of Adak, Alaska 08:43 UTC
12. 1.9 Andreanof Islands, Aleutian Islands, Alaska 08:43 UTC
13. 2.0 90 km W of Adak, Alaska 08:22 UTC
14. 2.1 90 km W of Adak, Alaska 08:19 UTC
15. 2.2 90 km W of Adak, Alaska 08:17 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 14:13 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.