132 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 136 km (85 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 85 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 2,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 89× the energy of this one
3. Magna, Utah 2020 M 5.7 63× the energy of this one
4. This earthquake M 4.5 about 85 tons of TNT
5. Around the size people start to feel M 3.0 this one released 180× 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 1,000 times the energy of this one.

Before 2016, the USGS record lists 195 earthquakes of M5 or more within 50 km; the five largest:

1. 7.3 88 km WSW of Adak, Alaska · 46 km NE of this epicentre Jul 7, 1929
2. 7.0 114 km WSW of Adak, Alaska · 35 km N of this epicentre Jul 5, 1929
3. 7.0 148 km WSW of Adak, Alaska · 39 km NW of this epicentre Mar 11, 1957
4. 6.9 151 km WSW of Adak, Alaska · 45 km NW of this epicentre May 15, 1993
5. 6.8 111 km SW of Adak, Alaska · 21 km NE of this epicentre Jan 4, 1912

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 51.1409, -178.1353. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.1 141 km WSW of Adak, Alaska 20:24 UTC
2. 3.6 97 km WSW of Adak, Alaska 16:07 UTC
3. 1.6 128 km WSW of Adak, Alaska 10:00 UTC
4. 1.9 Andreanof Islands, Aleutian Islands, Alaska 23:37 UTC
5. 1.6 118 km WSW of Adak, Alaska 09:14 UTC
6. 2.6 155 km SW of Adak, Alaska 12:43 UTC
7. 1.9 93 km WSW of Adak, Alaska 15:34 UTC
8. 1.9 119 km WSW of Adak, Alaska 14:09 UTC
9. 3.4 137 km WSW of Adak, Alaska 09:20 UTC
10. 2.8 136 km WSW of Adak, Alaska 20:41 UTC
11. 2.8 115 km WSW of Adak, Alaska 11:15 UTC
12. 1.8 Andreanof Islands, Aleutian Islands, Alaska 22:12 UTC
13. 1.5 148 km WSW of Adak, Alaska 22:03 UTC
14. 3.6 134 km WSW of Adak, Alaska 06:21 UTC
15. 3.5 109 km WSW of Adak, Alaska 18:49 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 20:50 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.