136 km SSW 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 21 km (13 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 4.7 on 2018-11-29 — about 1,400 times the energy of this one.

Before 2016, the USGS record lists 59 earthquakes of M5 or more within 50 km; the five largest:

1. 6.8 111 km SW of Adak, Alaska · 50 km NNW of this epicentre Jan 4, 1912
2. 6.5 144 km SW of Adak, Alaska · 48 km WNW of this epicentre Apr 16, 1927
3. 6.3 134 km SW of Adak, Alaska · 42 km NW of this epicentre Aug 3, 1972
4. 6.2 161 km SW of Adak, Alaska · 48 km W of this epicentre Dec 9, 1918
5. 6.2 101 km SW of Adak, Alaska · 46 km N of this epicentre Jun 2, 1940

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 50.8504, -177.7041. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.6 129 km SW of Adak, Alaska 23:46 UTC
2. 2.1 134 km SW of Adak, Alaska 11:51 UTC
3. 2.5 115 km SW of Adak, Alaska 11:35 UTC
4. 2.2 133 km SW of Adak, Alaska 04:30 UTC
5. 2.9 117 km SW of Adak, Alaska 14:34 UTC
6. 2.0 126 km SW of Adak, Alaska 16:55 UTC
7. 2.6 124 km SW of Adak, Alaska 15:34 UTC
8. 2.1 121 km SW of Adak, Alaska 00:35 UTC
9. 2.4 132 km SW of Adak, Alaska 12:12 UTC
10. 2.2 126 km SW of Adak, Alaska 08:31 UTC
11. 2.0 125 km SW of Adak, Alaska 07:17 UTC
12. 2.2 127 km SW of Adak, Alaska 06:55 UTC
13. 4.2 125 km SW of Adak, Alaska 06:41 UTC
14. 2.5 136 km SW of Adak, Alaska 06:05 UTC
15. 1.9 131 km SW of Adak, Alaska 05:49 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 08:34 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.