104 km ENE 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 it was probably too small to be felt, even directly above it. 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 7.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 22,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,000× the energy of this one
3. Magna, Utah 2020 M 5.7 710× the energy of this one
4. This earthquake M 3.8 about 7.6 tons of TNT
5. Around the size people start to feel M 3.0 this one released 16× 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 4.9 on 2016-10-20 — about 45 times the energy of this one.

Before 2016, the USGS record lists 10 earthquakes of M5 or more within 50 km; the five largest:

1. 5.8 66 km E of Atka, Alaska · 41 km WSW of this epicentre Jan 7, 1971
2. 5.7 78 km ENE of Atka, Alaska · 27 km W of this epicentre May 21, 1971
3. 5.7 89 km E of Atka, Alaska · 36 km SSW of this epicentre Mar 22, 1993
4. 5.5 78 km NE of Atka, Alaska · 38 km WNW of this epicentre May 24, 2011
5. 5.3 57 km E of Atka, Alaska · 48 km WSW of this epicentre Feb 13, 1988

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 52.4771, -172.7343. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.9 109 km E of Atka, Alaska 10:26 UTC
2. 2.8 121 km E of Atka, Alaska 00:58 UTC
3. 3.4 77 km ENE of Atka, Alaska 14:51 UTC
4. 2.9 97 km E of Atka, Alaska 23:46 UTC
5. 3.1 70 km E of Atka, Alaska 08:08 UTC
6. 3.0 74 km E of Atka, Alaska 07:20 UTC
7. 2.8 65 km E of Atka, Alaska 22:56 UTC
8. 2.7 71 km ENE of Atka, Alaska 18:39 UTC
9. 3.0 86 km ENE of Atka, Alaska 07:25 UTC
10. 4.0 107 km NE of Atka, Alaska 09:35 UTC
11. 3.2 110 km ENE of Atka, Alaska 20:52 UTC
12. 3.0 114 km ENE of Atka, Alaska 01:24 UTC
13. 3.3 79 km ENE of Atka, Alaska 11:04 UTC
14. 4.0 129 km E of Atka, Alaska 05:02 UTC
15. 3.3 95 km E of Atka, Alaska 16:31 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:44 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.