98 km SSW of Unalaska, Alaska

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 77 km (48 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 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.

For this area

The largest earthquake within 50 km since 2016 was M 5.4 on 2016-07-26 — about 180 times the energy of this one.

Before 2016, the USGS record lists 59 earthquakes of M5 or more within 50 km; the five largest:

1. 7.8 81 km E of Nikolski, Alaska · 44 km W of this epicentre Jul 2, 1965
2. 6.9 80 km E of Nikolski, Alaska · 46 km W of this epicentre Mar 24, 1980
3. 6.8 81 km ENE of Nikolski, Alaska · 49 km WNW of this epicentre Jan 13, 1955
4. 6.8 68 km SSW of Unalaska, Alaska · 31 km N of this epicentre Mar 29, 1957
5. 6.5 84 km E of Nikolski, Alaska · 41 km W of this epicentre Jan 13, 1955

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 53.0347, -166.9948. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 4.1 79 km S of Unalaska, Alaska 11:46 UTC
2. 2.0 67 km SSW of Unalaska, Alaska 11:24 UTC
3. 2.3 103 km S of Unalaska, Alaska 02:11 UTC
4. 2.5 93 km SSW of Unalaska, Alaska 20:42 UTC
5. 1.8 91 km SSW of Unalaska, Alaska 10:37 UTC
6. 2.7 62 km SSW of Unalaska, Alaska 00:58 UTC
7. 2.0 73 km SSW of Unalaska, Alaska 15:30 UTC
8. 1.8 68 km SSW of Unalaska, Alaska 17:20 UTC
9. 1.6 91 km SSW of Unalaska, Alaska 04:45 UTC
10. 2.6 82 km S of Unalaska, Alaska 20:04 UTC
11. 2.5 101 km E of Nikolski, Alaska 18:58 UTC
12. 4.4 136 km ESE of Nikolski, Alaska 09:08 UTC
13. 2.4 68 km SSW of Unalaska, Alaska 00:23 UTC
14. 1.7 82 km SW of Unalaska, Alaska 11:59 UTC
15. 2.2 84 km SSW of Unalaska, Alaska 18:02 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 05:00 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.