196 km WSW of Adak, 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 8 km (5 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 5.1 on 2017-01-18 — about 16,000 times the energy of this one.

Before 2016, the USGS record lists 179 earthquakes of M5 or more within 50 km; the five largest:

1. 7.2 238 km WSW of Adak, Alaska · 47 km W of this epicentre Mar 22, 1905
2. 7.2 162 km WSW of Adak, Alaska · 40 km NNE of this epicentre Mar 16, 1957
3. 7.2 207 km WSW of Adak, Alaska · 35 km NW of this epicentre Dec 19, 2007
4. 7.0 148 km WSW of Adak, Alaska · 48 km ENE of this epicentre Mar 11, 1957
5. 6.9 203 km WSW of Adak, Alaska · 32 km NW of this epicentre Mar 31, 1913

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 51.1176, -179.1910. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 4.2 204 km WSW of Adak, Alaska 21:31 UTC
2. 2.8 192 km WSW of Adak, Alaska 16:11 UTC
3. 3.9 214 km SW of Adak, Alaska 17:54 UTC
4. 2.4 184 km WSW of Adak, Alaska 04:27 UTC
5. 2.1 183 km WSW of Adak, Alaska 20:20 UTC
6. 3.8 220 km WSW of Adak, Alaska 08:21 UTC
7. 3.0 166 km WSW of Adak, Alaska 04:54 UTC
8. 3.2 220 km WSW of Adak, Alaska 07:32 UTC
9. 3.0 187 km WSW of Adak, Alaska 02:52 UTC
10. 3.1 172 km WSW of Adak, Alaska 02:31 UTC
11. 3.7 164 km WSW of Adak, Alaska 22:11 UTC
12. 2.9 158 km WSW of Adak, Alaska 16:12 UTC
13. 1.9 175 km WSW of Adak, Alaska 08:58 UTC
14. 2.4 178 km WSW of Adak, Alaska 15:21 UTC
15. 2.9 186 km WSW of Adak, Alaska 08:20 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 12:04 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.