222 km W of Adak, Alaska

Yes. A magnitude 4.0 earthquake was recorded 222 km W of Adak, Alaska at 00:12 UTC on 2018-06-21, 116 km deep.

2018-06-21 00:12 UTC · 116 km deep · released about 15 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: 2018-06-21 00:12 UTC
Magnitude: M 4.0 (mb)
Depth: 116 km below the surface
Felt: no reports yet
Status: Reviewed by a seismologist

USGS · last changed by USGS 1187 days ago · we first saw it 1187 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 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 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

Northridge, California 1994 M 6.7 11,000× the energy of this one
Mineral, Virginia 2011 M 5.8 500× the energy of this one
Magna, Utah 2020 M 5.7 350× the energy of this one
This earthquake M 4.0 about 15 tons of TNT
Around the size people start to feel M 3.0 this one released 32× 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 5.2 on 2016-11-23 — about 63 times the energy of this one.

Before 2016, the USGS record lists 39 earthquakes of M5 or more within 50 km; the five largest:

7.2 207 km WSW of Adak, Alaska · 50 km SSE of this epicentre Dec 19, 2007
6.7 237 km WSW of Adak, Alaska · 45 km S of this epicentre Oct 13, 1926
6.7 205 km WSW of Adak, Alaska · 31 km SE of this epicentre Oct 13, 1926
6.7 227 km WSW of Adak, Alaska · 37 km S of this epicentre Jun 2, 1955
6.7 221 km WSW of Adak, Alaska · 27 km S of this epicentre Jun 20, 1955

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

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

1.9 200 km W of Adak, Alaska 17:07 UTC
2.2 201 km W of Adak, Alaska 17:01 UTC
2.4 228 km WSW of Adak, Alaska 18:31 UTC
2.5 198 km W of Adak, Alaska 12:09 UTC
2.4 223 km W of Adak, Alaska 01:16 UTC
2.3 192 km W of Adak, Alaska 06:57 UTC
2.4 206 km W of Adak, Alaska 04:41 UTC
1.9 197 km W of Adak, Alaska 08:29 UTC
3.1 225 km W of Adak, Alaska 00:14 UTC
2.8 192 km WSW of Adak, Alaska 16:11 UTC
2.2 194 km W of Adak, Alaska 13:50 UTC
2.3 202 km W of Adak, Alaska 01:28 UTC
2.7 226 km W of Adak, Alaska 09:08 UTC
4.8 232 km W of Adak, Alaska 03:42 UTC
3.8 208 km W of Adak, Alaska 18:16 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 12:09 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.