40 km SSW 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 8 km (5 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 6.3 on 2016-03-12 — about 16,000 times the energy of this one.

Before 2016, the USGS record lists 91 earthquakes of M5 or more within 50 km; the five largest:

1. 8.0 1986 Atka, Alaska Earthquake · 45 km SW of this epicentre May 7, 1986
2. 6.8 57 km SSW of Atka, Alaska · 17 km S of this epicentre Nov 1, 1946
3. 6.6 62 km SSE of Atka, Alaska · 39 km SE of this epicentre Mar 10, 1957
4. 6.5 81 km SSW of Atka, Alaska · 42 km SW of this epicentre Sep 4, 2013
5. 6.1 65 km S of Atka, Alaska · 31 km SSE of this epicentre Jul 19, 1933

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 51.8530, -174.3983. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.6 11 km SW of Atka, Alaska 18:29 UTC
2. 0.5 16 km SW of Atka, Alaska 09:51 UTC
3. 1.7 15 km SSW of Atka, Alaska 08:44 UTC
4. 2.9 41 km SW of Atka, Alaska 17:10 UTC
5. 2.7 25 km SE of Atka, Alaska 08:03 UTC
6. 2.6 68 km S of Atka, Alaska 00:43 UTC
7. 2.9 82 km S of Atka, Alaska 17:18 UTC
8. 2.7 52 km SW of Atka, Alaska 08:17 UTC
9. 3.4 57 km SSW of Atka, Alaska 20:24 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:18 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.