199 km E 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 66 km (41 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 4.7 on 2017-11-09 — about 32 times the energy of this one.

Before 2016, the USGS record lists 66 earthquakes of M5 or more within 50 km; the five largest:

1. 7.3 Fox Islands, Aleutian Islands, Alaska · 37 km WNW of this epicentre Jun 24, 2011
2. 6.9 170 km E of Atka, Alaska · 37 km NW of this epicentre Sep 2, 2011
3. 6.2 179 km SW of Nikolski, Alaska · 46 km ESE of this epicentre Jun 4, 1956
4. 6.1 185 km ESE of Atka, Alaska · 18 km WSW of this epicentre Dec 6, 1930
5. 6.1 207 km ESE of Atka, Alaska · 31 km S of this epicentre Mar 13, 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 51.9314, -171.3290. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.7 176 km ESE of Atka, Alaska 13:48 UTC
2. 3.9 181 km WSW of Nikolski, Alaska 11:21 UTC
3. 2.7 173 km SW of Nikolski, Alaska 14:06 UTC
4. 2.5 165 km SW of Nikolski, Alaska 08:03 UTC
5. 2.8 165 km SW of Nikolski, Alaska 05:47 UTC
6. 3.5 182 km E of Atka, Alaska 03:12 UTC
7. 2.8 171 km E of Atka, Alaska 16:59 UTC
8. 3.0 174 km ESE of Atka, Alaska 21:01 UTC
9. 2.9 173 km WSW of Nikolski, Alaska 07:57 UTC
10. 4.1 177 km E of Atka, Alaska 06:53 UTC
11. 3.7 171 km SW of Nikolski, Alaska 08:19 UTC
12. 3.7 169 km ESE of Atka, Alaska 22:45 UTC
13. 3.0 167 km WSW of Nikolski, Alaska 08:41 UTC
14. 3.2 192 km SW of Nikolski, Alaska 04:07 UTC
15. 3.8 173 km ESE of Atka, Alaska 14:41 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:57 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.