201 km SSE 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 20 km (12 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 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 4.5 on 2017-01-10 — about 1,000 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

1. 6.0 234 km SSE of Atka, Alaska · 33 km S of this epicentre Nov 9, 1929
2. 5.6 198 km SSE of Atka, Alaska · 20 km ENE of this epicentre Mar 7, 2015
3. 5.5 232 km SSE of Atka, Alaska · 37 km SE of this epicentre Jul 13, 1981
4. 5.4 198 km SSE of Atka, Alaska · 4 km NW of this epicentre Feb 20, 2013
5. 5.2 181 km SSE of Atka, Alaska · 47 km NE of this epicentre Oct 12, 2006

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 50.4320, -173.5453. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.7 171 km S of Atka, Alaska 16:37 UTC
2. 2.7 178 km SSE of Atka, Alaska 16:13 UTC
3. 3.0 202 km SSE of Atka, Alaska 07:23 UTC
4. 2.8 203 km S of Atka, Alaska 22:03 UTC
5. 3.1 194 km SSE of Atka, Alaska 11:12 UTC
6. 3.0 195 km S of Atka, Alaska 13:56 UTC
7. 3.1 170 km SSE of Atka, Alaska 22:16 UTC
8. 2.6 171 km S of Atka, Alaska 21:36 UTC
9. 3.8 175 km SSE of Atka, Alaska 14:13 UTC
10. 3.1 205 km SSE of Atka, Alaska 13:14 UTC
11. 3.1 202 km SSE of Atka, Alaska 02:30 UTC
12. 2.5 164 km SSE of Atka, Alaska 23:43 UTC
13. 2.8 177 km SSE of Atka, Alaska 19:36 UTC
14. 2.9 159 km SSE of Atka, Alaska 13:15 UTC
15. 3.5 206 km SSE of Atka, Alaska 16:29 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 14:34 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.