140 km S of McCarthy, Alaska

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. 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 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
3. Around the size people start to feel M 3.0 11× the energy of this one
4. This earthquake M 2.3 about 85 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 4.3 on 2017-11-13 — about 1,000 times the energy of this one.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

1. 6.7 163 km W of Yakutat, Alaska · 45 km S of this epicentre Apr 16, 1970
2. 5.8 162 km WNW of Yakutat, Alaska · 27 km SSE of this epicentre Sep 19, 1933
3. 5.5 164 km S of McCarthy, Alaska · 23 km SSE of this epicentre Apr 30, 1964

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 60.1760, -142.6510. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 0.9 107 km S of McCarthy, Alaska 03:42 UTC
2. 1.2 101 km S of McCarthy, Alaska 01:17 UTC
3. 1.5 94 km S of McCarthy, Alaska 11:57 UTC
4. 1.1 123 km S of McCarthy, Alaska 20:08 UTC
5. 1.1 99 km S of McCarthy, Alaska 16:09 UTC
6. 1.1 109 km S of McCarthy, Alaska 22:53 UTC
7. 1.2 113 km S of McCarthy, Alaska 09:53 UTC
8. 1.6 101 km S of McCarthy, Alaska 03:57 UTC
9. 1.1 107 km S of McCarthy, Alaska 19:20 UTC
10. 1.2 93 km S of McCarthy, Alaska 04:04 UTC
11. 2.1 134 km S of McCarthy, Alaska 19:42 UTC
12. 1.0 117 km S of McCarthy, Alaska 14:49 UTC
13. 1.1 128 km SSE of McCarthy, Alaska 06:13 UTC
14. 1.8 93 km S of McCarthy, Alaska 04:15 UTC
15. 0.6 104 km S of McCarthy, Alaska 17:16 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 23:06 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

Revisions

USGS refines a solution as more stations report. Every change we have seen is listed here.

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.