155 km SSE of Perryville, Alaska

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 18 km (11 mi) from the epicentre. Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

How big was it?

This earthquake released about 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
3. Around the size people start to feel M 3.0 11× the energy of this one
4. This earthquake M 2.3 about 85 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.

For this area

The largest earthquake within 50 km since 2016 was M 5.5 on 2021-07-29 — about 63,000 times the energy of this one.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

1. 6.5 183 km SSE of Perryville, Alaska · 42 km SSW of this epicentre Jul 1, 1967
2. 6.2 143 km SE of Perryville, Alaska · 20 km NNE of this epicentre Mar 25, 1927
3. 5.9 182 km SE of Perryville, Alaska · 35 km ESE of this epicentre Dec 23, 1938
4. 5.5 160 km SE of Perryville, Alaska · 39 km ENE of this epicentre Mar 10, 2012
5. 5.4 139 km SSE of Perryville, Alaska · 22 km WNW of this epicentre Jan 1, 1991

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 54.7276, -157.8424. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 114 km SSE of Perryville, Alaska 10:55 UTC
2. 3.9 125 km SE of Perryville, Alaska 22:38 UTC
3. 3.4 142 km SE of Perryville, Alaska 13:00 UTC
4. 2.3 124 km SE of Perryville, Alaska 06:53 UTC
5. 2.6 130 km SE of Perryville, Alaska 01:16 UTC
6. 2.7 136 km SSE of Perryville, Alaska 13:33 UTC
7. 3.0 121 km SE of Perryville, Alaska 19:20 UTC
8. 2.6 128 km SE of Perryville, Alaska 04:17 UTC
9. 2.4 117 km SE of Perryville, Alaska 19:15 UTC
10. 3.3 134 km SE of Perryville, Alaska 17:40 UTC
11. 3.1 198 km SSE of Perryville, Alaska 11:18 UTC
12. 2.5 179 km SSE of Perryville, Alaska 15:20 UTC
13. 3.4 141 km SE of Perryville, Alaska 15:19 UTC
14. 2.9 142 km SSE of Perryville, Alaska 06:34 UTC
15. 2.1 146 km SSE of Perryville, Alaska 07:12 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 15:43 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

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.