121 km SSW of Atka, 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 16 km (10 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 240 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.6 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 63,000× the energy of this one
2. Magna, Utah 2020 M 5.7 45,000× the energy of this one
3. Around the size people start to feel M 3.0 4× the energy of this one
4. This earthquake M 2.6 about 240 lb of TNT

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 5.2 on 2018-07-09 — about 7,900 times the energy of this one.

Before 2016, the USGS record lists 137 earthquakes of M5 or more within 50 km; the five largest:

1. 8.0 1986 Atka, Alaska Earthquake · 36 km NNE of this epicentre May 7, 1986
2. 7.0 153 km SE of Adak, Alaska · 43 km SSW of this epicentre Jan 17, 1903
3. 7.0 101 km SW of Atka, Alaska · 37 km NNW of this epicentre Aug 30, 2013
4. 6.9 100 km ESE of Adak, Alaska · 38 km NNW of this epicentre Oct 13, 1926
5. 6.8 99 km SW of Atka, Alaska · 33 km NNW of this epicentre Mar 19, 1957

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 51.2301, -175.0143. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 Andreanof Islands, Aleutian Islands, Alaska 15:27 UTC
2. 1.8 102 km SW of Atka, Alaska 01:40 UTC
3. 3.7 97 km SW of Atka, Alaska 14:28 UTC
4. 1.7 97 km ESE of Adak, Alaska 21:48 UTC
5. 2.5 98 km SW of Atka, Alaska 09:06 UTC
6. 1.7 85 km SW of Atka, Alaska 09:04 UTC
7. 1.8 92 km SW of Atka, Alaska 07:54 UTC
8. 2.6 103 km SSW of Atka, Alaska 16:30 UTC
9. 2.4 107 km SW of Atka, Alaska 05:03 UTC
10. 2.1 120 km SSW of Atka, Alaska 04:45 UTC
11. 2.0 119 km SSW of Atka, Alaska 04:24 UTC
12. 2.2 94 km SW of Atka, Alaska 15:10 UTC
13. 2.0 113 km SSW of Atka, Alaska 19:38 UTC
14. 2.2 105 km ESE of Adak, Alaska 08:19 UTC
15. 1.7 97 km SW of Atka, Alaska 10:18 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 04:56 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.