QuakeIndex

Earthquake · reviewed by a seismologist

M 6.3mww

108 km SSW of Adak, Alaska

· 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 589 days ago

This was a strong earthquake. Damage is likely near the epicentre and it is felt over a wide area. 7 people have reported feeling it to USGS.

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.

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.

For this area

The largest earthquake within 50 km in our catalogue was M 6.3 on 2018-08-23.

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

On USGS

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