195 km E of Atka, 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 53 km (33 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 2.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 63,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2,800× the energy of this one
3. Magna, Utah 2020 M 5.7 2,000× the energy of this one
4. This earthquake M 3.5 about 2.7 tons of TNT
5. Around the size people start to feel M 3.0 this one released 5.6× 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 2018-08-25 — about 4,000 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. 7.3 Fox Islands, Aleutian Islands, Alaska · 33 km WNW of this epicentre Jun 24, 2011
2. 6.9 170 km E of Atka, Alaska · 34 km NW of this epicentre Sep 2, 2011
3. 6.1 185 km ESE of Atka, Alaska · 15 km SW of this epicentre Dec 6, 1930
4. 6.1 207 km ESE of Atka, Alaska · 31 km S of this epicentre Mar 13, 1957
5. 6.1 157 km ESE of Atka, Alaska · 41 km W of this epicentre Jul 13, 1959

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 51.9366, -171.3869. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.1 191 km SW of Nikolski, Alaska 00:35 UTC
2. 3.0 174 km E of Atka, Alaska 02:26 UTC
3. 3.2 185 km ESE of Atka, Alaska 16:47 UTC
4. 3.4 181 km WSW of Nikolski, Alaska 00:02 UTC
5. 3.3 179 km SW of Nikolski, Alaska 00:01 UTC
6. 2.2 178 km SW of Nikolski, Alaska 17:28 UTC
7. 3.2 163 km E of Atka, Alaska 23:39 UTC
8. 3.8 189 km ESE of Atka, Alaska 15:01 UTC
9. 2.8 190 km E of Atka, Alaska 23:39 UTC
10. 2.7 178 km WSW of Nikolski, Alaska 15:32 UTC
11. 3.8 182 km ESE of Atka, Alaska 15:02 UTC
12. 2.4 180 km WSW of Nikolski, Alaska 23:09 UTC
13. 3.3 188 km SW of Nikolski, Alaska 16:38 UTC
14. 2.7 178 km WSW of Nikolski, Alaska 01:38 UTC
15. 3.2 171 km SW of Nikolski, Alaska 03:42 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:16 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.