157 km SW of Nikolski, 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 72 km (45 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 5.9 on 2018-08-25 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 75 earthquakes of M5 or more within 50 km; the five largest:

1. 6.6 135 km SW of Nikolski, Alaska · 42 km ESE of this epicentre Dec 23, 1906
2. 6.2 179 km SW of Nikolski, Alaska · 32 km S of this epicentre Jun 4, 1956
3. 6.2 Fox Islands, Aleutian Islands, Alaska · 48 km S of this epicentre Mar 10, 1957
4. 6.1 Fox Islands, Aleutian Islands, Alaska · 31 km SSW of this epicentre Jan 11, 1961
5. 6.0 177 km WSW of Nikolski, Alaska · 44 km WNW of this epicentre Aug 19, 1925

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 52.0683, -170.6863. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.0 168 km SW of Nikolski, Alaska 20:41 UTC
2. 3.2 Fox Islands, Aleutian Islands, Alaska 02:37 UTC
3. 3.4 164 km WSW of Nikolski, Alaska 01:00 UTC
4. 3.5 148 km SW of Nikolski, Alaska 22:10 UTC
5. 2.8 Fox Islands, Aleutian Islands, Alaska 15:34 UTC
6. 2.3 176 km SW of Nikolski, Alaska 10:16 UTC
7. 2.7 Fox Islands, Aleutian Islands, Alaska 04:41 UTC
8. 3.0 150 km SW of Nikolski, Alaska 10:07 UTC
9. 3.7 180 km WSW of Nikolski, Alaska 06:29 UTC
10. 2.1 176 km WSW of Nikolski, Alaska 10:16 UTC
11. 3.7 178 km SW of Nikolski, Alaska 04:03 UTC
12. 2.6 171 km SW of Nikolski, Alaska 11:16 UTC
13. 3.3 184 km SW of Nikolski, Alaska 23:25 UTC
14. 3.1 165 km WSW of Nikolski, Alaska 22:04 UTC
15. 2.6 163 km SW of Nikolski, Alaska 11:08 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:37 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.