240 km SSW 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 63 km (39 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 2.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 63,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 2,800× the energy of this one
3. Magna, Utah 2020 M 5.7 2,000× the energy of this one
4. This earthquake M 3.5 about 2.7 tons of TNT
5. Around the size people start to feel M 3.0 this one released 5.6× 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 2018-08-10 — about 89 times the energy of this one.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

1. 6.8 Andreanof Islands, Aleutian Islands, Alaska · 32 km WNW of this epicentre Jun 22, 1913
2. 6.0 254 km SW of Adak, Alaska · 35 km W of this epicentre Jul 8, 1929
3. 6.0 257 km SW of Adak, Alaska · 48 km WNW 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 50.0052, -178.3422. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.1 257 km SSW of Adak, Alaska 01:27 UTC
2. 2.5 232 km SSW of Adak, Alaska 17:37 UTC
3. 3.2 236 km SSW of Adak, Alaska 18:59 UTC
4. 2.8 244 km SSW of Adak, Alaska 04:35 UTC
5. 2.5 192 km SSW of Adak, Alaska 14:16 UTC
6. 2.6 271 km SSW of Adak, Alaska 03:49 UTC
7. 2.9 234 km SW of Adak, Alaska 09:50 UTC
8. 3.9 265 km SSW of Adak, Alaska 06:13 UTC
9. 2.9 229 km SW of Adak, Alaska 05:17 UTC
10. 2.4 249 km SSW of Adak, Alaska 06:49 UTC
11. 2.7 193 km SSW of Adak, Alaska 09:06 UTC
12. 2.8 204 km SSW of Adak, Alaska 08:34 UTC
13. 2.9 246 km SSW of Adak, Alaska 15:12 UTC
14. 2.5 217 km SW of Adak, Alaska 21:07 UTC
15. 3.0 222 km SW of Adak, Alaska 09:44 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 08:35 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.