111 km SW 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, people at rest would likely notice it out to about 141 km (88 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 120 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.6 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 1,400× the energy of this one
2. Mineral, Virginia 2011 M 5.8 63× the energy of this one
3. Magna, Utah 2020 M 5.7 45× the energy of this one
4. This earthquake M 4.6 about 120 tons of TNT
5. Around the size people start to feel M 3.0 this one released 250× 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 4.9 on 2017-01-11 — about 2.8 times the energy of this one.

Before 2016, the USGS record lists 161 earthquakes of M5 or more within 50 km; the five largest:

1. 7.9 77 km WSW of Adak, Alaska · 43 km NNE of this epicentre Jun 10, 1996
2. 7.3 88 km WSW of Adak, Alaska · 32 km N of this epicentre Jul 7, 1929
3. 7.0 114 km WSW of Adak, Alaska · 38 km NW of this epicentre Jul 5, 1929
4. 7.0 69 km SW of Adak, Alaska · 42 km ENE of this epicentre May 2, 1971
5. 6.9 78 km WSW of Adak, Alaska · 45 km NNE of this epicentre Mar 20, 1999

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 51.1940, -177.8098. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.7 76 km WSW of Adak, Alaska 05:18 UTC
2. 2.9 72 km WSW of Adak, Alaska 19:15 UTC
3. 1.8 66 km SW of Adak, Alaska 15:40 UTC
4. 1.9 105 km WSW of Adak, Alaska 18:16 UTC
5. 2.1 115 km WSW of Adak, Alaska 14:38 UTC
6. 2.5 114 km WSW of Adak, Alaska 23:10 UTC
7. 2.4 123 km WSW of Adak, Alaska 15:31 UTC
8. 1.8 126 km WSW of Adak, Alaska 18:17 UTC
9. 2.2 103 km SW of Adak, Alaska 13:25 UTC
10. 2.1 101 km SW of Adak, Alaska 09:54 UTC
11. 1.5 71 km SW of Adak, Alaska 01:53 UTC
12. 1.9 98 km SW of Adak, Alaska 06:51 UTC
13. 2.8 122 km WSW of Adak, Alaska 23:56 UTC
14. 1.5 76 km WSW of Adak, Alaska 04:10 UTC
15. 2.5 100 km SSW of Adak, Alaska 12:59 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 10:58 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.