Alaska Peninsula

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 94 km (58 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 21 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.1 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 7,900× the energy of this one
2. Mineral, Virginia 2011 M 5.8 350× the energy of this one
3. Magna, Utah 2020 M 5.7 250× the energy of this one
4. This earthquake M 4.1 about 21 tons of TNT
5. Around the size people start to feel M 3.0 this one released 45× 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 in our catalogue was M 4.5 on 2017-03-28 — about 4 times the energy of this one.

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 56.5875, -156.4840. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.9 Alaska Peninsula 12:41 UTC
2. 2.0 124 km E of Chignik, Alaska 10:11 UTC
3. 1.7 97 km SSE of Ugashik, Alaska 02:14 UTC
4. 2.0 131 km E of Chignik, Alaska 05:13 UTC
5. 2.5 124 km E of Chignik, Alaska 20:29 UTC
6. 2.2 109 km W of Akhiok, Alaska 06:39 UTC
7. 2.3 114 km SSE of Ugashik, Alaska 03:34 UTC
8. 2.1 85 km SSE of Ugashik, Alaska 18:16 UTC
9. 2.3 94 km SE of Ugashik, Alaska 07:23 UTC
10. 2.6 115 km SSE of Ugashik, Alaska 01:19 UTC
11. 2.9 129 km E of Chignik, Alaska 14:25 UTC
12. 2.7 129 km WSW of Akhiok, Alaska 16:49 UTC
13. 1.6 92 km SE of Ugashik, Alaska 07:30 UTC
14. 2.3 101 km ENE of Chignik, Alaska 03:59 UTC
15. 1.6 112 km ENE of Chignik, Alaska 07:38 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 00:17 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.