110 km E of Chignik, Alaska

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 96 km (60 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 since 2016 was M 4.5 on 2017-03-28 — about 4 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

1. 7.0 113 km ESE of Chignik, Alaska · 45 km SSW of this epicentre May 4, 1923
2. 6.8 117 km SSE of Ugashik, Alaska · 41 km NNE of this epicentre May 29, 2015
3. 6.4 77 km ESE of Chignik, Alaska · 37 km WSW of this epicentre Mar 24, 1972
4. 6.4 104 km SSE of Ugashik, Alaska · 46 km N of this epicentre May 20, 1979
5. 6.3 112 km E of Chignik, Alaska · 6 km S of this epicentre Feb 25, 1953

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 56.2387, -156.6199. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.3 106 km SSE of Ugashik, Alaska 01:26 UTC
2. 1.6 118 km SE of Ugashik, Alaska 00:45 UTC
3. 2.3 128 km E of Chignik, Alaska 06:20 UTC
4. 2.1 135 km E of Chignik, Alaska 10:21 UTC
5. 3.1 115 km ESE of Chignik, Alaska 10:12 UTC
6. 2.3 112 km E of Chignik, Alaska 10:19 UTC
7. 2.6 96 km E of Chignik, Alaska 05:15 UTC
8. 2.0 100 km SSE of Ugashik, Alaska 03:57 UTC
9. 2.2 77 km E of Chignik, Alaska 10:01 UTC
10. 2.8 131 km ESE of Chignik, Alaska 19:08 UTC
11. 2.6 127 km SSE of Ugashik, Alaska 05:52 UTC
12. 2.0 122 km E of Chignik, Alaska 15:53 UTC
13. 2.5 120 km SSE of Ugashik, Alaska 07:40 UTC
14. 2.5 Alaska Peninsula 08:31 UTC
15. 1.9 123 km SSE of Ugashik, Alaska 07:16 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 02:38 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.