210 km W of Adak, 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 5.2 on 2016-11-23 — about 63 times the energy of this one.

Before 2016, the USGS record lists 21 earthquakes of M5 or more within 50 km; the five largest:

1. 6.7 205 km WSW of Adak, Alaska · 47 km SSE of this epicentre Oct 13, 1926
2. 6.6 174 km W of Adak, Alaska · 38 km ESE of this epicentre Apr 16, 2008
3. 6.4 187 km W of Adak, Alaska · 26 km ESE of this epicentre Apr 15, 2008
4. 6.2 230 km W of Adak, Alaska · 20 km WNW of this epicentre Apr 29, 2007
5. 5.9 194 km W of Adak, Alaska · 44 km SSE of this epicentre Jun 22, 1978

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 51.9611, -179.6969. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.5 198 km W of Adak, Alaska 12:09 UTC
2. 2.4 223 km W of Adak, Alaska 01:16 UTC
3. 2.3 192 km W of Adak, Alaska 06:57 UTC
4. 2.4 206 km W of Adak, Alaska 04:41 UTC
5. 1.9 197 km W of Adak, Alaska 08:29 UTC
6. 3.1 225 km W of Adak, Alaska 00:14 UTC
7. 2.7 175 km W of Adak, Alaska 18:46 UTC
8. 2.2 194 km W of Adak, Alaska 13:50 UTC
9. 2.3 202 km W of Adak, Alaska 01:28 UTC
10. 2.7 226 km W of Adak, Alaska 09:08 UTC
11. 4.8 232 km W of Adak, Alaska 03:42 UTC
12. 3.8 208 km W of Adak, Alaska 18:16 UTC
13. 2.4 212 km W of Adak, Alaska 07:55 UTC
14. 2.6 207 km WNW of Adak, Alaska 00:39 UTC
15. 2.8 201 km W of Adak, Alaska 04:02 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:37 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.