QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2mb

237 km SSW of Adak, Alaska

· 34 km deep · released about 30 tons of TNT

Felt it? Tell USGS Check my area
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 4.2 (mb)
Depth
34 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1150 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

How big was it?

This earthquake released about 30 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 5,600× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 250× the energy of this one
  3. Magna, Utah 2020 M 5.7 180× the energy of this one
  4. This earthquake M 4.2 about 30 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 63× 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 50.1099, -178.5455. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.6 240 km SW of Adak, Alaska
  2. 3.8 249 km SSW of Adak, Alaska
  3. 2.5 Andreanof Islands, Aleutian Islands, Alaska
  4. 2.5 Andreanof Islands, Aleutian Islands, Alaska
  5. 2.1 203 km SW of Adak, Alaska
  6. 2.4 227 km SSW of Adak, Alaska
  7. 2.7 245 km SW of Adak, Alaska
  8. 2.3 238 km SSW of Adak, Alaska
  9. 2.6 217 km SSW of Adak, Alaska
  10. 3.5 237 km SSW of Adak, Alaska
  11. 3.4 204 km SSW of Adak, Alaska
  12. 2.8 239 km SSW of Adak, Alaska
  13. 1.9 211 km SSW of Adak, Alaska
  14. 2.1 242 km SW of Adak, Alaska
  15. 1.9 254 km SW 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.