183 km SE of Atka, Alaska

Yes. A magnitude 4.2 earthquake was recorded 183 km SE of Atka, Alaska at 02:41 UTC on 2018-08-21, 27 km deep.

2018-08-21 02:41 UTC · 27 km deep · released about 30 tons of TNT

Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.

When: 2018-08-21 02:41 UTC
Magnitude: M 4.2 (mb)
Depth: 27 km below the surface
Felt: no reports yet
Nearest mapped fault: Alaska-Aleutian subduction zone, 1 km from its surface trace — near is not the same as on
Status: Reviewed by a seismologist

USGS · last changed by USGS 1186 days ago · we first saw it 1186 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 109 km (68 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 30 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.

Northridge, California 1994 M 6.7 5,600× the energy of this one
Mineral, Virginia 2011 M 5.8 250× the energy of this one
Magna, Utah 2020 M 5.7 180× the energy of this one
This earthquake M 4.2 about 30 tons of TNT
Around the size people start to feel M 3.0 this one released 63× 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

Tied for the largest within 50 km (31 mi) since 2016, with M 4.2 on 2016-04-05.

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

6.9 182 km SSE of Atka, Alaska · 20 km WSW of this epicentre Jan 27, 1906
5.8 174 km SSE of Atka, Alaska · 39 km WSW of this epicentre Apr 1, 1957
5.8 161 km SSE of Atka, Alaska · 40 km W of this epicentre Apr 2, 1957
5.8 165 km SSE of Atka, Alaska · 44 km W of this epicentre Apr 2, 1957
5.8 150 km SSE of Atka, Alaska · 41 km WNW of this epicentre Apr 2, 1957

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

Map loads when it scrolls into view

Aftershocks so far

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

2.9 184 km SSE of Atka, Alaska 19:19 UTC
1.7 136 km SE of Atka, Alaska 11:46 UTC
2.5 204 km SSE of Atka, Alaska 11:20 UTC
2.8 187 km SE of Atka, Alaska 09:22 UTC
2.8 190 km SSE of Atka, Alaska 16:21 UTC
2.1 184 km SE of Atka, Alaska 17:18 UTC
3.1 185 km SSE of Atka, Alaska 04:17 UTC
3.0 192 km SE of Atka, Alaska 19:44 UTC
2.3 176 km SSE of Atka, Alaska 13:26 UTC
3.2 165 km SE of Atka, Alaska 07:55 UTC
2.8 155 km SE of Atka, Alaska 09:49 UTC
2.7 138 km SE of Atka, Alaska 09:57 UTC
2.2 180 km SSE of Atka, Alaska 21:10 UTC
2.2 140 km SE of Atka, Alaska 11:59 UTC
2.0 163 km SE of Atka, Alaska 20:09 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 15:18 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.