179 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 89 km (55 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 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 16,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
3. Magna, Utah 2020 M 5.7 500× the energy of this one
4. This earthquake M 3.9 about 11 tons of TNT
5. Around the size people start to feel M 3.0 this one released 22× 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 1,000 times the energy of this one.

Before 2016, the USGS record lists 38 earthquakes of M5 or more within 50 km; the five largest:

1. 7.3 Fox Islands, Aleutian Islands, Alaska · 45 km SSW of this epicentre Jun 24, 2011
2. 6.9 170 km E of Atka, Alaska · 30 km SSW of this epicentre Sep 2, 2011
3. 6.2 173 km WSW of Nikolski, Alaska · 24 km NE of this epicentre Jan 14, 1968
4. 6.1 188 km E of Atka, Alaska · 23 km SSE of this epicentre Jan 4, 1968
5. 6.0 177 km WSW of Nikolski, Alaska · 30 km SE of this epicentre Aug 19, 1925

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 52.4314, -171.6026. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.1 145 km ENE of Atka, Alaska 15:01 UTC
2. 2.9 170 km WSW of Nikolski, Alaska 21:48 UTC
3. 3.2 169 km WSW of Nikolski, Alaska 03:18 UTC
4. 3.2 166 km WSW of Nikolski, Alaska 23:07 UTC
5. 2.8 171 km WSW of Nikolski, Alaska 06:43 UTC
6. 3.1 172 km WSW of Nikolski, Alaska 19:07 UTC
7. 4.1 173 km W of Nikolski, Alaska 14:39 UTC
8. 3.5 163 km W of Nikolski, Alaska 14:34 UTC
9. 3.2 178 km E of Atka, Alaska 20:00 UTC
10. 3.9 167 km WSW of Nikolski, Alaska 08:28 UTC
11. 3.2 172 km WSW of Nikolski, Alaska 19:31 UTC
12. 2.9 178 km E of Atka, Alaska 09:03 UTC
13. 2.9 171 km ENE of Atka, Alaska 05:54 UTC
14. 2.8 189 km WSW of Nikolski, Alaska 10:07 UTC
15. 2.8 184 km E of Atka, Alaska 14:46 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:54 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.