54 km SSE 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 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 5.1 on 2016-08-27 — about 63 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

1. 6.0 98 km ESE of Perryville, Alaska · 48 km SSE of this epicentre Jan 2, 1985
2. 5.8 46 km S of Chignik, Alaska · 16 km WNW of this epicentre Feb 21, 1972
3. 5.5 51 km SSE of Chignik, Alaska · 8 km W of this epicentre Feb 24, 1972
4. 5.1 34 km S of Chignik, Alaska · 28 km NW of this epicentre Sep 5, 1994

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 55.8336, -158.0886. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.4 42 km SSE of Chignik, Alaska 15:35 UTC
2. 2.6 88 km SSE of Chignik, Alaska 09:03 UTC
3. 2.8 Alaska Peninsula 08:25 UTC
4. 2.3 40 km E of Perryville, Alaska 05:38 UTC
5. 2.9 55 km ESE of Chignik, Alaska 08:01 UTC
6. 2.1 57 km ESE of Perryville, Alaska 22:46 UTC
7. 2.3 90 km ESE of Perryville, Alaska 20:29 UTC
8. 3.1 69 km SE of Perryville, Alaska 20:31 UTC
9. 2.4 Alaska Peninsula 19:19 UTC
10. 2.0 52 km ESE of Perryville, Alaska 10:25 UTC
11. 2.5 64 km SE of Perryville, Alaska 23:46 UTC
12. 2.9 80 km SSE of Chignik, Alaska 05:09 UTC
13. 3.0 59 km ESE of Chignik, Alaska 09:43 UTC
14. 2.9 33 km ESE of Chignik, Alaska 06:06 UTC
15. 2.6 40 km SSE of Chignik, Alaska 08:11 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 18:53 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.