168 km ESE of Chignik, 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 7.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 22,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,000× the energy of this one
3. Magna, Utah 2020 M 5.7 710× the energy of this one
4. This earthquake M 3.8 about 7.6 tons of TNT
5. Around the size people start to feel M 3.0 this one released 16× 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 55.5122, -156.0915. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.5 155 km SE of Chignik, Alaska 07:13 UTC
2. 2.6 166 km ESE of Chignik, Alaska 01:41 UTC
3. 2.4 162 km SW of Akhiok, Alaska 11:42 UTC
4. 3.3 150 km ESE of Chignik, Alaska 08:44 UTC
5. 2.4 south of Alaska 04:20 UTC
6. 2.0 154 km ESE of Chignik, Alaska 02:09 UTC
7. 2.6 182 km SE of Chignik, Alaska 06:44 UTC
8. 2.7 135 km ESE of Chignik, Alaska 21:31 UTC
9. 2.4 194 km SE of Chignik, Alaska 07:21 UTC
10. 3.4 163 km SE of Chignik, Alaska 05:46 UTC
11. 2.5 134 km ESE of Chignik, Alaska 18:57 UTC
12. 2.3 183 km ESE of Chignik, Alaska 19:23 UTC
13. 2.2 155 km ESE of Chignik, Alaska 05:20 UTC
14. 2.2 145 km ESE of Chignik, Alaska 08:12 UTC
15. 2.3 159 km SE of Chignik, Alaska 15:30 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 15:36 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 4.8 on 2021-07-29 — it released about 32 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.