104 km WSW 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 81 km (50 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 7.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 22,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,000× the energy of this one
3. Magna, Utah 2020 M 5.7 710× the energy of this one
4. This earthquake M 3.8 about 7.6 tons of TNT
5. Around the size people start to feel M 3.0 this one released 16× 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 5.2 on 2017-05-06 — about 130 times the energy of this one.

Before 2016, the USGS record lists 45 earthquakes of M5 or more within 50 km; the five largest:

1. 6.9 80 km SW of Nikolski, Alaska · 46 km ESE of this epicentre Mar 9, 1957
2. 6.8 79 km SW of Nikolski, Alaska · 45 km ESE of this epicentre Jan 28, 1967
3. 6.2 91 km SW of Nikolski, Alaska · 43 km ESE of this epicentre Feb 10, 1953
4. 6.2 87 km SW of Nikolski, Alaska · 42 km ESE of this epicentre Oct 23, 1957
5. 6.1 88 km SW of Nikolski, Alaska · 33 km ESE of this epicentre Sep 2, 1950

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 52.4650, -170.1973. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.9 81 km SW of Nikolski, Alaska 12:00 UTC
2. 2.5 145 km WSW of Nikolski, Alaska 05:09 UTC
3. 2.5 85 km W of Nikolski, Alaska 00:00 UTC
4. 3.0 96 km SW of Nikolski, Alaska 14:02 UTC
5. 2.5 122 km SW of Nikolski, Alaska 20:19 UTC
6. 4.2 Fox Islands, Aleutian Islands, Alaska 20:12 UTC
7. 3.1 126 km SW of Nikolski, Alaska 20:11 UTC
8. 2.0 70 km WSW of Nikolski, Alaska 01:37 UTC
9. 3.4 128 km WSW of Nikolski, Alaska 11:53 UTC
10. 3.1 83 km SW of Nikolski, Alaska 14:48 UTC
11. 2.8 131 km WSW of Nikolski, Alaska 06:39 UTC
12. 3.4 133 km SW of Nikolski, Alaska 15:28 UTC
13. 2.6 130 km SW of Nikolski, Alaska 09:34 UTC
14. 3.1 128 km SW of Nikolski, Alaska 08:38 UTC
15. 4.9 130 km WSW of Nikolski, Alaska 08:16 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:14 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.