136 km ESE of Nikolski, Alaska

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 104 km (65 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 21 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.1 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 7,900× the energy of this one
2. Mineral, Virginia 2011 M 5.8 350× the energy of this one
3. Magna, Utah 2020 M 5.7 250× the energy of this one
4. This earthquake M 4.1 about 21 tons of TNT
5. Around the size people start to feel M 3.0 this one released 45× 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 2017-05-24 — about 500 times the energy of this one.

Before 2016, the USGS record lists 49 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 Fox Islands, Aleutian Islands, Alaska · 44 km SW of this epicentre Jan 1, 1902
2. 6.5 127 km E of Nikolski, Alaska · 17 km NNW of this epicentre Oct 13, 2009
3. 6.4 118 km E of Nikolski, Alaska · 22 km NW of this epicentre Mar 15, 1957
4. 6.4 123 km ESE of Nikolski, Alaska · 13 km W of this epicentre Oct 13, 2009
5. 6.3 110 km SE of Nikolski, Alaska · 49 km WSW of this epicentre Sep 25, 1942

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 52.6058, -166.9204. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 162 km ESE of Nikolski, Alaska 12:00 UTC
2. 2.2 127 km S of Unalaska, Alaska 21:16 UTC
3. 2.7 124 km S of Unalaska, Alaska 16:30 UTC
4. 2.3 127 km S of Unalaska, Alaska 11:18 UTC
5. 2.3 120 km S of Unalaska, Alaska 11:17 UTC
6. 4.0 110 km SSW of Unalaska, Alaska 10:24 UTC
7. 1.9 123 km S of Unalaska, Alaska 04:11 UTC
8. 2.2 102 km SSW of Unalaska, Alaska 23:55 UTC
9. 2.5 134 km S of Unalaska, Alaska 23:38 UTC
10. 2.5 133 km S of Unalaska, Alaska 21:08 UTC
11. 1.9 130 km S of Unalaska, Alaska 08:51 UTC
12. 1.8 118 km S of Unalaska, Alaska 06:15 UTC
13. 2.7 143 km ESE of Nikolski, Alaska 01:55 UTC
14. 1.9 99 km E of Nikolski, Alaska 21:07 UTC
15. 3.4 137 km ESE of Nikolski, Alaska 01:57 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 11:05 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.