119 km E of Chignik, 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 25 km (16 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 1.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 130,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 5,600× the energy of this one
3. Magna, Utah 2020 M 5.7 4,000× the energy of this one
4. This earthquake M 3.3 about 1.3 tons of TNT
5. Around the size people start to feel M 3.0 this one released 2.8× 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 63 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. 6.8 117 km SSE of Ugashik, Alaska · 26 km N of this epicentre May 29, 2015
2. 6.4 104 km SSE of Ugashik, Alaska · 36 km NNW of this epicentre May 20, 1979
3. 6.3 112 km E of Chignik, Alaska · 21 km SSW of this epicentre Feb 25, 1953
4. 6.1 132 km E of Chignik, Alaska · 22 km SE of this epicentre Sep 13, 1911
5. 6.1 118 km ESE of Chignik, Alaska · 48 km S of this epicentre Mar 16, 1940

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 56.3571, -156.4739. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 6.9 112 km E of Chignik, Alaska 09:10 UTC
2. 2.4 106 km E of Chignik, Alaska 06:52 UTC
3. 3.0 119 km E of Chignik, Alaska 09:01 UTC
4. 1.8 109 km SSE of Ugashik, Alaska 11:36 UTC
5. 2.7 118 km WSW of Akhiok, Alaska 03:59 UTC
6. 3.2 99 km ENE of Chignik, Alaska 18:19 UTC
7. 3.2 96 km ENE of Chignik, Alaska 14:58 UTC
8. 2.2 118 km ESE of Chignik, Alaska 01:38 UTC
9. 2.2 119 km ESE of Chignik, Alaska 00:10 UTC
10. 1.8 124 km SE of Ugashik, Alaska 23:23 UTC
11. 1.9 90 km ENE of Chignik, Alaska 12:40 UTC
12. 1.8 92 km E of Chignik, Alaska 04:15 UTC
13. 2.1 119 km SSE of Ugashik, Alaska 15:56 UTC
14. 1.8 118 km ENE of Chignik, Alaska 05:19 UTC
15. 2.3 117 km E of Chignik, Alaska 18:59 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:23 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.