112 km S 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 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
3. Around the size people start to feel M 3.0 5.6× the energy of this one
4. This earthquake M 2.5 about 170 lb of TNT

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 500,000 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. 6.6 89 km S of Atka, Alaska · 25 km NNW of this epicentre Mar 10, 1957
2. 6.1 65 km S of Atka, Alaska · 47 km N of this epicentre Jul 19, 1933
3. 6.1 87 km S of Atka, Alaska · 25 km N of this epicentre Jun 9, 1983
4. 6.1 72 km S of Atka, Alaska · 43 km NNW of this epicentre Nov 2, 2008
5. 5.9 81 km S of Atka, Alaska · 31 km NNW of this epicentre May 9, 1986

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 51.1898, -174.1498. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.9 89 km S of Atka, Alaska 19:00 UTC
2. 2.6 152 km S of Atka, Alaska 10:15 UTC
3. 2.1 93 km SSE of Atka, Alaska 22:59 UTC
4. 4.1 91 km S of Atka, Alaska 05:55 UTC
5. 2.7 78 km SSE of Atka, Alaska 01:15 UTC
6. 2.3 147 km S of Atka, Alaska 18:10 UTC
7. 3.3 105 km S of Atka, Alaska 18:13 UTC
8. 2.3 94 km S of Atka, Alaska 03:13 UTC
9. 3.7 94 km SSW of Atka, Alaska 12:02 UTC
10. 2.9 100 km SSW of Atka, Alaska 03:40 UTC
11. 5.2 97 km SSW of Atka, Alaska 02:42 UTC
12. 3.8 95 km SSW of Atka, Alaska 01:28 UTC
13. 3.5 105 km SSW of Atka, Alaska 00:14 UTC
14. 2.3 145 km S of Atka, Alaska 02:51 UTC
15. 2.3 139 km SSW of Atka, Alaska 01:43 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 04:38 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.