123 km E of McCarthy, 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 44 km (27 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 1,900 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.2 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 180,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 7,900× the energy of this one
3. Magna, Utah 2020 M 5.7 5,600× the energy of this one
4. This earthquake M 3.2 about 1,900 lb of TNT
5. Around the size people start to feel M 3.0 this one released 2× 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 4.9 on 2021-05-09 — about 350 times the energy of this one.

Before 2016, the USGS record lists 10 earthquakes of M5 or more within 50 km; the five largest:

1. 6.1 109 km E of McCarthy, Alaska · 34 km SSW of this epicentre Jul 7, 1920
2. 5.7 152 km E of McCarthy, Alaska · 35 km SE of this epicentre Jun 26, 2001
3. 5.5 87 km ENE of McCarthy, Alaska · 39 km WNW of this epicentre Nov 23, 1987
4. 5.4 140 km SSE of Alcan Border, Alaska · 19 km ESE of this epicentre Jun 10, 1972
5. 5.4 136 km SSE of Alcan Border, Alaska · 27 km E of this epicentre Mar 30, 1983

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 61.5306, -140.6046. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 2.0 119 km ESE of McCarthy, Alaska 06:19 UTC
2. 1.5 117 km ESE of McCarthy, Alaska 06:02 UTC
3. 2.0 118 km ESE of McCarthy, Alaska 05:16 UTC
4. 2.0 119 km ESE of McCarthy, Alaska 01:34 UTC
5. 1.7 119 km ESE of McCarthy, Alaska 00:30 UTC
6. 2.0 128 km E of McCarthy, Alaska 22:43 UTC
7. 1.9 105 km ESE of McCarthy, Alaska 21:33 UTC
8. 1.6 120 km ESE of McCarthy, Alaska 02:24 UTC
9. 1.5 117 km E of McCarthy, Alaska 02:04 UTC
10. 1.6 114 km E of McCarthy, Alaska 20:29 UTC
11. 1.8 121 km ESE of McCarthy, Alaska 17:58 UTC
12. 1.7 116 km E of McCarthy, Alaska 10:35 UTC
13. 1.6 124 km ESE of McCarthy, Alaska 11:04 UTC
14. 1.5 122 km ESE of McCarthy, Alaska 07:02 UTC
15. 1.5 123 km ESE of McCarthy, Alaska 06:25 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 18:27 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.