QuakeIndex

Earthquake · reviewed by a seismologist

M 7.9mww

261 km SE of Chiniak, Alaska

· 14 km deep · released about 11 megatons 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 7.9 (mww)
Depth
14 km below the surface
Felt
2383 reports · strongest reported intensity VIII
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 689 days ago

This was a major earthquake. Serious damage is likely near the epicentre. Follow official information from USGS and local authorities. 2383 people have reported feeling it to USGS.

How big was it?

This earthquake released about 11 megatons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 8.9 would have released about 32 times as much.

  1. Great Alaska earthquake 1964 M 9.2 89× the energy of this one
  2. Tōhoku, Japan 2011 M 9.1 63× the energy of this one
  3. This earthquake M 7.9 about 11 megatons of TNT
  4. Ridgecrest, California 2019 M 7.1 this one released 16× more
  5. Loma Prieta, California 1989 M 6.9 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.

Where

Epicentre 56.0039, -149.1658. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.4 255 km SE of Chiniak, Alaska
  2. 3.5 226 km SE of Chiniak, Alaska
  3. 3.0 240 km SE of Chiniak, Alaska
  4. 3.7 235 km SE of Chiniak, Alaska
  5. 3.6 223 km SE of Chiniak, Alaska
  6. 3.6 242 km SE of Chiniak, Alaska
  7. 3.5 246 km SE of Chiniak, Alaska
  8. 3.8 222 km SE of Chiniak, Alaska
  9. 4.2 227 km SE of Chiniak, Alaska
  10. 3.6 296 km SE of Chiniak, Alaska
  11. 3.6 239 km SE of Chiniak, Alaska
  12. 4.1 245 km SE of Chiniak, Alaska
  13. 3.7 221 km SE of Chiniak, Alaska
  14. 3.7 235 km SE of Chiniak, Alaska
  15. 3.3 254 km SE of Chiniak, 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 4.3 on 2017-10-30.

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

On USGS

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