145 km SE of Chignik, Alaska

Yes. A magnitude 4.2 earthquake was recorded 145 km SE of Chignik, Alaska at 08:15 UTC on 2021-07-29, 18 km deep.

2021-07-29 08:15 UTC · 18 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: 2021-07-29 08:15 UTC
Magnitude: M 4.2 (ml)
Depth: 18 km below the surface
Felt: no reports yet
Measured shaking: intensity II (ShakeMap)
Status: Reviewed by a seismologist

USGS · last changed by USGS 1868 days ago · we first saw it 1868 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 111 km (69 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

The largest earthquake within 50 km since 2016 was M 5.9 on 2021-07-29 — about 350 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

7.0 164 km SE of Chignik, Alaska · 27 km E of this epicentre Sep 4, 1989
6.7 121 km SE of Chignik, Alaska · 24 km NW of this epicentre Feb 13, 1979
6.6 128 km SE of Chignik, Alaska · 35 km NNE of this epicentre Jul 28, 1934
6.2 189 km SE of Chignik, Alaska · 45 km SSE of this epicentre Mar 18, 1945
6.0 168 km SE of Chignik, Alaska · 26 km ESE of this epicentre Nov 16, 1938

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

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

2.4 136 km SE of Chignik, Alaska 17:19 UTC
2.5 125 km SE of Chignik, Alaska 16:34 UTC
3.0 152 km SE of Chignik, Alaska 16:28 UTC
2.6 151 km SE of Chignik, Alaska 16:26 UTC
2.6 157 km SSE of Chignik, Alaska 16:17 UTC
5.3 155 km SE of Chignik, Alaska 16:09 UTC
2.5 144 km SSE of Chignik, Alaska 15:19 UTC
3.6 150 km SE of Chignik, Alaska 15:13 UTC
2.6 133 km SE of Chignik, Alaska 15:12 UTC
2.9 129 km SE of Chignik, Alaska 15:06 UTC
2.7 143 km SE of Chignik, Alaska 15:02 UTC
3.0 Alaska Peninsula 14:48 UTC
2.8 149 km SE of Perryville, Alaska 14:45 UTC
2.8 141 km SE of Chignik, Alaska 14:42 UTC
3.0 186 km SE of Chignik, Alaska 14:20 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 18:45 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.