78 km N of Atka, 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 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 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 11,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 500× the energy of this one
3. Magna, Utah 2020 M 5.7 350× the energy of this one
4. This earthquake M 4.0 about 15 tons of TNT
5. Around the size people start to feel M 3.0 this one released 32× 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 4.8 on 2017-12-28 — about 16 times the energy of this one.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

1. 5.9 42 km NNW of Atka, Alaska · 46 km SSW of this epicentre Mar 27, 1971
2. 5.8 116 km NNE of Atka, Alaska · 47 km NE of this epicentre Dec 28, 2004
3. 5.5 76 km N of Atka, Alaska · 18 km E of this epicentre Mar 27, 1992
4. 5.5 104 km N of Atka, Alaska · 27 km NNE of this epicentre Nov 19, 2011
5. 5.4 50 km NW of Atka, Alaska · 50 km SW of this epicentre May 5, 2011

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 52.8998, -174.2577. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.7 44 km NNW of Atka, Alaska 16:46 UTC
2. 2.7 42 km NNW of Atka, Alaska 16:46 UTC
3. 2.9 39 km NW of Atka, Alaska 16:46 UTC
4. 2.7 45 km N of Atka, Alaska 09:09 UTC
5. 3.7 68 km NNE of Atka, Alaska 09:59 UTC
6. 1.9 41 km NNW of Atka, Alaska 09:48 UTC
7. 2.9 54 km N of Atka, Alaska 23:55 UTC
8. 2.0 34 km NNW of Atka, Alaska 02:38 UTC
9. 3.2 44 km NNW of Atka, Alaska 15:28 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 19:05 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.