QuakeIndex

Earthquake · reviewed by a seismologist

M 5.6mww

172 km ENE of Atka, Alaska

· 15 km deep · released about 3.8 kilotons of TNT

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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 5.6 (mww)
Depth
15 km below the surface
Felt
no reports yet
Measured shaking
intensity V (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

How big was it?

This earthquake released about 3.8 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.6 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 45× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2× the energy of this one
  3. Magna, Utah 2020 M 5.7 1.4× the energy of this one
  4. This earthquake M 5.6 about 3.8 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 7,900× 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.

Where

Epicentre 52.5259, -171.7222. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.2 166 km WSW of Nikolski, Alaska
  2. 3.8 166 km W of Nikolski, Alaska
  3. 4.1 173 km W of Nikolski, Alaska
  4. 3.5 163 km W of Nikolski, Alaska
  5. 3.2 178 km E of Atka, Alaska
  6. 2.9 178 km E of Atka, Alaska
  7. 2.9 171 km ENE of Atka, Alaska
  8. 2.9 175 km E of Atka, Alaska
  9. 3.1 173 km E of Atka, Alaska
  10. 2.5 176 km E of Atka, Alaska
  11. 2.9 176 km E of Atka, Alaska
  12. 2.7 172 km E of Atka, Alaska
  13. 2.8 181 km E of Atka, Alaska
  14. 3.4 169 km E of Atka, Alaska
  15. 3.5 165 km W of Nikolski, 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.

For this area

The largest earthquake within 50 km in our catalogue was M 5.6 on 2023-10-12.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

On USGS

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