198 km SW of Nikolski, Alaska

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

How big was it?

This earthquake released about 5.4 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.7 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 32,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,400× the energy of this one
3. Magna, Utah 2020 M 5.7 1,000× the energy of this one
4. This earthquake M 3.7 about 5.4 tons of TNT
5. Around the size people start to feel M 3.0 this one released 11× 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.

Where

Epicentre 51.7226, -170.9982. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 3.5 157 km SW of Nikolski, Alaska 10:16 UTC
2. 2.6 191 km ESE of Atka, Alaska 09:44 UTC
3. 3.7 197 km SW of Nikolski, Alaska 17:10 UTC
4. 3.5 186 km SW of Nikolski, Alaska 04:52 UTC
5. 3.1 182 km SW of Nikolski, Alaska 14:35 UTC
6. 3.1 196 km ESE of Atka, Alaska 12:32 UTC
7. 3.2 194 km SW of Nikolski, Alaska 03:17 UTC
8. 3.2 186 km E of Atka, Alaska 13:23 UTC
9. 2.7 Fox Islands, Aleutian Islands, Alaska 11:01 UTC
10. 3.2 193 km SW of Nikolski, Alaska 12:22 UTC
11. 3.5 160 km SW of Nikolski, Alaska 23:35 UTC
12. 2.7 172 km SW of Nikolski, Alaska 00:30 UTC
13. 2.8 162 km SW of Nikolski, Alaska 11:46 UTC
14. 3.4 185 km E of Atka, Alaska 16:58 UTC
15. 2.8 182 km WSW of Nikolski, Alaska 15:34 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 18:12 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

For this area

The largest earthquake within 50 km in our catalogue was M 5.9 on 2018-08-25 — it released about 2,000 times the energy of this one.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

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.