QuakeIndex

Earthquake · reviewed by a seismologist

M 4.6mb

164 km S of Atka, Alaska

Yes. A magnitude 4.6 earthquake was recorded 164 km S of Atka, Alaska at 12:54 UTC on 2023-04-22, 10 km deep.

· 10 km deep · released about 120 tons of TNT

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10 km30 km60 km120 km N
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
Magnitude
M 4.6 (mb)
Depth
10 km below the surface
Felt
no reports yet
Measured shaking
intensity I (ShakeMap)
Nearest mapped fault
Alaska-Aleutian subduction zone, 7 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1230 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 149 km (93 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 120 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.6 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 1,400× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 63× the energy of this one
  3. Magna, Utah 2020 M 5.7 45× the energy of this one
  4. This earthquake M 4.6 about 120 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 250× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.4 on 2022-07-24.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.0 153 km SE of Adak, Alaska · 47 km WNW of this epicentre
  2. 6.6 208 km S of Atka, Alaska · 47 km SSE of this epicentre
  3. 6.1 193 km SE of Adak, Alaska · 39 km SW of this epicentre
  4. 5.8 131 km S of Atka, Alaska · 33 km NNE of this epicentre
  5. 5.6 178 km SE of Adak, Alaska · 35 km WSW of this epicentre

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 50.7334, -174.5119. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.9 196 km SSW of Atka, Alaska
  2. 2.8 174 km S of Atka, Alaska
  3. 1.9 159 km SSW of Atka, Alaska
  4. 2.0 188 km S of Atka, Alaska
  5. 2.3 187 km S of Atka, Alaska
  6. 2.3 159 km S of Atka, Alaska
  7. 1.9 140 km S of Atka, Alaska
  8. 3.1 199 km SSW of Atka, Alaska
  9. 2.9 195 km S of Atka, Alaska
  10. 2.7 168 km SSW of Atka, Alaska
  11. 2.6 170 km S of Atka, Alaska
  12. 2.1 132 km S of Atka, Alaska
  13. 2.7 190 km S of Atka, Alaska
  14. 2.9 193 km S of Atka, Alaska
  15. 2.8 194 km S of Atka, Alaska

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

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.