208 km S of Unalaska, 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 169 km (105 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 240 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.8 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 710× the energy of this one
2. Mineral, Virginia 2011 M 5.8 32× the energy of this one
3. Magna, Utah 2020 M 5.7 22× the energy of this one
4. This earthquake M 4.8 about 240 tons of TNT
5. Around the size people start to feel M 3.0 this one released 500× 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 2019-08-03 — about 4 times the energy of this one.

Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 203 km SSE of Unalaska, Alaska · 39 km ENE of this epicentre Aug 22, 1940
2. 6.5 183 km S of Unalaska, Alaska · 31 km NW of this epicentre Apr 19, 1957
3. 6.0 221 km S of Unalaska, Alaska · 13 km SSE of this epicentre Mar 17, 1957
4. 6.0 218 km SE of Nikolski, Alaska · 36 km SSW of this epicentre Aug 7, 2004
5. 5.4 214 km ESE of Nikolski, Alaska · 19 km SW of this epicentre Apr 8, 1975

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 52.0284, -166.0280. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.3 200 km SSE of Unalaska, Alaska 12:29 UTC
2. 3.4 169 km S of Unalaska, Alaska 20:33 UTC
3. 4.2 165 km S of Unalaska, Alaska 20:33 UTC
4. 2.8 181 km SSE of Unalaska, Alaska 16:44 UTC
5. 3.1 179 km SSE of Unalaska, Alaska 15:15 UTC
6. 2.9 167 km SSE of Unalaska, Alaska 13:57 UTC
7. 2.7 207 km S of Unalaska, Alaska 16:10 UTC
8. 2.6 191 km S of Unalaska, Alaska 09:11 UTC
9. 2.8 192 km SSE of Unalaska, Alaska 22:14 UTC
10. 3.3 208 km ESE of Nikolski, Alaska 02:23 UTC
11. 2.8 213 km SSE of Unalaska, Alaska 19:35 UTC
12. 3.2 196 km ESE of Nikolski, Alaska 01:27 UTC
13. 3.4 207 km SE of Nikolski, Alaska 21:49 UTC
14. 2.6 185 km SSE of Unalaska, Alaska 23:18 UTC
15. 2.9 south of the Aleutian Islands 03:46 UTC

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