151 km ENE of Atka, Alaska

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes 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 680 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 22,000× the energy of this one
2. Magna, Utah 2020 M 5.7 16,000× the energy of this one
3. Around the size people start to feel M 3.0 1.4× the energy of this one
4. This earthquake M 2.9 about 680 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 4.5 on 2019-05-20 — about 250 times the energy of this one.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

1. 6.9 170 km E of Atka, Alaska · 44 km SSE of this epicentre Sep 2, 2011
2. 6.2 173 km WSW of Nikolski, Alaska · 45 km ENE of this epicentre Jan 14, 1968
3. 6.1 188 km E of Atka, Alaska · 49 km SE of this epicentre Jan 4, 1968
4. 6.0 182 km E of Atka, Alaska · 44 km SE of this epicentre Mar 24, 1957
5. 5.7 162 km E of Atka, Alaska · 42 km SSE of this epicentre Oct 25, 2011

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 52.5141, -172.0314. Map © OpenStreetMap contributors.

Aftershocks so far

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

1. 4.3 185 km E of Atka, Alaska 14:20 UTC
2. 2.2 132 km E of Atka, Alaska 19:06 UTC
3. 3.1 128 km E of Atka, Alaska 05:27 UTC
4. 3.3 139 km E of Atka, Alaska 14:21 UTC
5. 3.6 118 km ENE of Atka, Alaska 03:34 UTC
6. 2.2 127 km ENE of Atka, Alaska 01:48 UTC
7. 3.3 172 km E of Atka, Alaska 03:14 UTC
8. 2.7 171 km E of Atka, Alaska 01:36 UTC
9. 2.8 121 km E of Atka, Alaska 00:58 UTC
10. 3.1 139 km E of Atka, Alaska 08:05 UTC
11. 3.2 178 km E of Atka, Alaska 04:15 UTC
12. 3.5 171 km E of Atka, Alaska 00:01 UTC
13. 3.8 183 km E of Atka, Alaska 16:50 UTC
14. 4.0 129 km E of Atka, Alaska 05:02 UTC
15. 3.4 174 km E of Atka, Alaska 02:31 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 07:43 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.