QuakeIndex

Earthquake · reviewed by a seismologist

M 6.3mww

108 km SSW of Adak, Alaska

Yes. A magnitude 6.3 earthquake was recorded 108 km SSW of Adak, Alaska at 19:57 UTC on 2024-12-08, 18 km deep. 7 people have reported feeling it to USGS.

· 18 km deep · released about 43 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 6.3 (mww)
Depth
18 km below the surface
Felt
7 reports · strongest reported intensity IV
Measured shaking
intensity III (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 636 days ago

This was a strong earthquake. Damage is likely near the epicentre and it is felt over a wide area.

At this magnitude and depth, people at rest would likely notice it out to about 407 km (253 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 43 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 7.3 would have released about 32 times as much.

  1. Ridgecrest, California 2019 M 7.1 16× the energy of this one
  2. Loma Prieta, California 1989 M 6.9 7.9× the energy of this one
  3. Northridge, California 1994 M 6.7 4× the energy of this one
  4. This earthquake M 6.3 about 43 kilotons of TNT
  5. Mineral, Virginia 2011 M 5.8 this one released 5.6× more
  6. Magna, Utah 2020 M 5.7 this one released 7.9× 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

Tied for the largest within 50 km (31 mi) since 2016, with M 6.3 on 2018-08-23.

Before 2016, the USGS record lists 69 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 75 km S of Adak, Alaska · 47 km ENE of this epicentre
  2. 7.0 69 km SW of Adak, Alaska · 45 km N of this epicentre
  3. 6.8 90 km SSW of Adak, Alaska · 26 km ENE of this epicentre
  4. 6.6 85 km SSW of Adak, Alaska · 31 km ENE of this epicentre
  5. 6.4 76 km SSW of Adak, Alaska · 32 km NNE 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 51.0018, -177.3278. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 5.5 132 km SSW of Adak, Alaska
  2. 6.1 126 km SSW of Adak, Alaska
  3. 4.0 119 km SSW of Adak, Alaska
  4. 2.4 120 km SSW of Adak, Alaska
  5. 3.6 123 km SSW of Adak, Alaska
  6. 3.3 115 km SSW of Adak, Alaska
  7. 4.5 120 km SSW of Adak, Alaska
  8. 5.2 122 km SSW of Adak, Alaska
  9. 3.2 126 km SSW of Adak, Alaska
  10. 2.3 118 km SSW of Adak, Alaska
  11. 2.3 109 km SSW of Adak, Alaska
  12. 5.2 121 km SSW of Adak, Alaska
  13. 5.0 124 km SSW of Adak, Alaska
  14. 3.1 109 km SSW of Adak, Alaska
  15. 3.5 125 km SSW of Adak, 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.