144 km SSW 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 71 km (44 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 4.6 on 2016-01-05 — about 22 times the energy of this one.

Before 2016, the USGS record lists 63 earthquakes of M5 or more within 50 km; the five largest:

1. 6.6 135 km SW of Nikolski, Alaska · 30 km NW of this epicentre Dec 23, 1906
2. 6.0 119 km SSW of Nikolski, Alaska · 26 km N of this epicentre Mar 29, 1931
3. 6.0 128 km SW of Nikolski, Alaska · 48 km NW of this epicentre Jun 1, 1945
4. 6.0 101 km SSW of Nikolski, Alaska · 44 km NNE of this epicentre Feb 9, 1953
5. 6.0 100 km SSW of Nikolski, Alaska · 46 km NNE of this epicentre Mar 24, 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 51.7757, -169.8200. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.0 112 km SSW of Nikolski, Alaska 08:18 UTC
2. 3.1 104 km SSW of Nikolski, Alaska 05:39 UTC
3. 3.0 105 km SSW of Nikolski, Alaska 05:16 UTC
4. 2.5 111 km SSW of Nikolski, Alaska 02:25 UTC
5. 3.2 164 km SW of Nikolski, Alaska 00:02 UTC
6. 4.0 115 km SSW of Nikolski, Alaska 03:05 UTC
7. 3.9 113 km SSW of Nikolski, Alaska 03:03 UTC
8. 3.0 137 km SSW of Nikolski, Alaska 10:31 UTC
9. 2.9 117 km SSW of Nikolski, Alaska 05:00 UTC
10. 2.3 118 km SSW of Nikolski, Alaska 09:56 UTC
11. 4.1 171 km SW of Nikolski, Alaska 16:25 UTC
12. 2.7 105 km SSW of Nikolski, Alaska 09:02 UTC
13. 2.7 159 km SSW of Nikolski, Alaska 19:16 UTC
14. 4.1 108 km SSW of Nikolski, Alaska 06:02 UTC
15. 3.4 111 km SSW of Nikolski, Alaska 07:48 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 10:43 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.