125 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 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 340 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.7 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 45,000× the energy of this one
2. Magna, Utah 2020 M 5.7 32,000× the energy of this one
3. Around the size people start to feel M 3.0 2.8× the energy of this one
4. This earthquake M 2.7 about 340 lb of TNT

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 2,000 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 · 30 km SW of this epicentre Jul 7, 1920
2. 5.7 152 km E of McCarthy, Alaska · 32 km ESE of this epicentre Jun 26, 2001
3. 5.5 87 km ENE of McCarthy, Alaska · 42 km WNW of this epicentre Nov 23, 1987
4. 5.4 140 km SSE of Alcan Border, Alaska · 16 km E of this epicentre Jun 10, 1972
5. 5.4 136 km SSE of Alcan Border, Alaska · 27 km ENE 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 61.4875, -140.5782. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 1.7 96 km E of McCarthy, Alaska 08:13 UTC
2. 1.7 96 km E of McCarthy, Alaska 20:04 UTC
3. 1.6 99 km E of McCarthy, Alaska 10:00 UTC
4. 1.5 151 km E of McCarthy, Alaska 23:37 UTC
5. 2.1 119 km E of McCarthy, Alaska 16:51 UTC
6. 1.5 132 km ESE of McCarthy, Alaska 21:19 UTC
7. 1.5 131 km ESE of McCarthy, Alaska 21:19 UTC
8. 2.1 Southern Yukon Territory, Canada 10:26 UTC
9. 1.5 133 km ESE of McCarthy, Alaska 05:30 UTC
10. 2.5 120 km E of McCarthy, Alaska 19:37 UTC
11. 2.1 120 km E of McCarthy, Alaska 23:34 UTC
12. 2.3 121 km E of McCarthy, Alaska 12:22 UTC
13. 2.0 122 km E of McCarthy, Alaska 12:56 UTC
14. 2.1 123 km E of McCarthy, Alaska 12:21 UTC
15. 3.3 121 km E of McCarthy, Alaska 13:54 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 22:34 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.