248 km SW of Adak, 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 14 km (9 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 340 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.7 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 45,000× the energy of this one
2. Magna, Utah 2020 M 5.7 32,000× the energy of this one
3. Around the size people start to feel M 3.0 2.8× the energy of this one
4. This earthquake M 2.7 about 340 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 4.8 on 2018-08-10 — about 1,400 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

1. 6.8 Andreanof Islands, Aleutian Islands, Alaska · 4 km SSE of this epicentre Jun 22, 1913
2. 6.0 207 km SW of Adak, Alaska · 45 km NNE of this epicentre Feb 7, 1926
3. 6.0 254 km SW of Adak, Alaska · 7 km SSW of this epicentre Jul 8, 1929
4. 6.0 257 km SW of Adak, Alaska · 15 km W of this epicentre Jul 3, 1957

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 50.1063, -178.7872. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.8 244 km SSW of Adak, Alaska 23:58 UTC
2. 2.4 237 km SW of Adak, Alaska 00:41 UTC
3. 2.6 270 km SW of Adak, Alaska 10:13 UTC
4. 2.1 262 km SW of Adak, Alaska 14:59 UTC
5. 4.0 250 km SSW of Adak, Alaska 13:46 UTC
6. 2.6 262 km SW of Adak, Alaska 18:40 UTC
7. 2.2 239 km SW of Adak, Alaska 15:29 UTC
8. 2.3 243 km SSW of Adak, Alaska 15:56 UTC
9. 3.5 240 km SSW of Adak, Alaska 00:51 UTC
10. 3.0 244 km SW of Adak, Alaska 03:15 UTC
11. 3.1 264 km SW of Adak, Alaska 21:16 UTC
12. 2.4 244 km SSW of Adak, Alaska 21:41 UTC
13. 3.0 274 km SW of Adak, Alaska 00:11 UTC
14. 2.6 280 km SW of Adak, Alaska 14:38 UTC
15. 3.5 268 km SSW of Adak, Alaska 06:34 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 16:47 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.