154 km SE 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 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 16,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
3. Magna, Utah 2020 M 5.7 500× the energy of this one
4. This earthquake M 3.9 about 11 tons of TNT
5. Around the size people start to feel M 3.0 this one released 22× 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 55.2268, -156.8352. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.7 157 km SE of Chignik, Alaska 06:46 UTC
2. 2.2 150 km SE of Perryville, Alaska 05:15 UTC
3. 2.4 126 km SE of Chignik, Alaska 05:09 UTC
4. 2.5 south of Alaska 22:37 UTC
5. 3.3 156 km SSE of Chignik, Alaska 22:00 UTC
6. 2.4 134 km SSE of Chignik, Alaska 17:58 UTC
7. 4.0 135 km SSE of Chignik, Alaska 09:54 UTC
8. 2.4 129 km SE of Chignik, Alaska 05:46 UTC
9. 2.8 139 km SE of Chignik, Alaska 03:22 UTC
10. 2.3 159 km SE of Chignik, Alaska 15:30 UTC
11. 2.6 158 km SE of Chignik, Alaska 12:45 UTC
12. 2.5 190 km SE of Chignik, Alaska 08:53 UTC
13. 3.3 159 km SSE of Chignik, Alaska 08:59 UTC
14. 3.7 156 km SE of Chignik, Alaska 06:04 UTC
15. 3.3 152 km SSE of Chignik, Alaska 14:50 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 10:59 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 2021-07-29 — it released about 1,000 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.