144 km SE of Perryville, 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 1,900 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.2 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 180,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 7,900× the energy of this one
3. Magna, Utah 2020 M 5.7 5,600× the energy of this one
4. This earthquake M 3.2 about 1,900 lb of TNT
5. Around the size people start to feel M 3.0 this one released 2× 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 55.0470, -157.4331. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.0 117 km SE of Perryville, Alaska 00:10 UTC
2. 2.3 136 km SE of Perryville, Alaska 21:57 UTC
3. 2.3 137 km SE of Perryville, Alaska 21:52 UTC
4. 2.3 147 km SE of Perryville, Alaska 19:36 UTC
5. 3.0 167 km SE of Perryville, Alaska 19:29 UTC
6. 2.5 119 km SE of Perryville, Alaska 16:26 UTC
7. 1.9 120 km SE of Perryville, Alaska 16:20 UTC
8. 3.7 139 km SE of Perryville, Alaska 15:40 UTC
9. 3.8 149 km SSE of Chignik, Alaska 15:28 UTC
10. 2.3 143 km SE of Perryville, Alaska 15:19 UTC
11. 3.1 137 km SE of Perryville, Alaska 12:58 UTC
12. 2.6 134 km SE of Perryville, Alaska 11:03 UTC
13. 2.8 Alaska Peninsula 08:34 UTC
14. 2.5 116 km SE of Perryville, Alaska 08:29 UTC
15. 2.5 141 km SE of Perryville, Alaska 07:34 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 13:49 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 8.2 on 2021-07-29 — it released about 32,000,000 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.