141 km ESE 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 19 km (12 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 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
3. Around the size people start to feel M 3.0 5.6× the energy of this one
4. This earthquake M 2.5 about 170 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 5.4 on 2016-07-26 — about 22,000 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. 7.0 Fox Islands, Aleutian Islands, Alaska · 36 km W of this epicentre Jan 1, 1902
2. 6.7 103 km SE of Nikolski, Alaska · 48 km W of this epicentre Feb 20, 1916
3. 6.5 183 km S of Unalaska, Alaska · 46 km ESE of this epicentre Apr 19, 1957
4. 6.5 127 km E of Nikolski, Alaska · 35 km N of this epicentre Oct 13, 2009
5. 6.4 118 km E of Nikolski, Alaska · 38 km NNW of this epicentre Mar 15, 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 52.4407, -166.9287. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.2 153 km ESE of Nikolski, Alaska 07:19 UTC
2. 3.2 169 km ESE of Nikolski, Alaska 20:55 UTC
3. 2.1 147 km SE of Nikolski, Alaska 23:11 UTC
4. 1.9 171 km SE of Nikolski, Alaska 11:02 UTC
5. 1.9 Fox Islands, Aleutian Islands, Alaska 13:16 UTC
6. 2.5 145 km ESE of Nikolski, Alaska 07:18 UTC
7. 2.3 155 km ESE of Nikolski, Alaska 17:52 UTC
8. 1.8 131 km S of Unalaska, Alaska 12:10 UTC
9. 2.5 Fox Islands, Aleutian Islands, Alaska 15:53 UTC
10. 2.7 161 km ESE of Nikolski, Alaska 13:03 UTC
11. 1.9 148 km S of Unalaska, Alaska 02:20 UTC
12. 2.1 141 km S of Unalaska, Alaska 02:57 UTC
13. 2.2 154 km ESE of Nikolski, Alaska 01:03 UTC
14. 2.0 147 km ESE of Nikolski, Alaska 04:52 UTC
15. 2.1 166 km ESE of Nikolski, Alaska 03:25 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:22 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.