219 km ESE 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 680 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 22,000× the energy of this one
2. Magna, Utah 2020 M 5.7 16,000× the energy of this one
3. Around the size people start to feel M 3.0 1.4× the energy of this one
4. This earthquake M 2.9 about 680 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.

Where

Epicentre 51.9091, -166.1159. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 204 km SE of Nikolski, Alaska 00:41 UTC
2. 2.5 224 km SE of Nikolski, Alaska 16:33 UTC
3. 3.1 193 km SSE of Unalaska, Alaska 08:34 UTC
4. 2.8 199 km SSE of Unalaska, Alaska 14:34 UTC
5. 2.6 196 km SE of Nikolski, Alaska 07:04 UTC
6. 2.9 197 km S of Unalaska, Alaska 12:53 UTC
7. 2.6 181 km ESE of Nikolski, Alaska 09:44 UTC
8. 2.8 199 km SE of Nikolski, Alaska 02:44 UTC
9. 2.9 190 km S of Unalaska, Alaska 01:51 UTC
10. 2.6 209 km S of Unalaska, Alaska 17:43 UTC
11. 3.4 195 km S of Unalaska, Alaska 23:49 UTC
12. 2.6 203 km ESE of Nikolski, Alaska 07:44 UTC
13. 3.2 200 km ESE of Nikolski, Alaska 16:58 UTC
14. 4.2 213 km S of Unalaska, Alaska 11:55 UTC
15. 2.3 219 km SE of Nikolski, Alaska 15:30 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 18:10 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 5.2 on 2019-08-03 — it released about 2,800 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.