QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2mb

128 km SE of Perryville, Alaska

· 40 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
40 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1151 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 55.1311, -157.6540. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.6 132 km SE of Perryville, Alaska
  2. 2.8 Alaska Peninsula
  3. 2.6 97 km SE of Perryville, Alaska
  4. 2.3 90 km ESE of Perryville, Alaska
  5. 2.6 113 km SE of Perryville, Alaska
  6. 2.4 99 km SE of Perryville, Alaska
  7. 3.2 115 km SE of Perryville, Alaska
  8. 2.7 165 km SE of Perryville, Alaska
  9. 2.3 125 km SE of Perryville, Alaska
  10. 3.5 109 km SE of Perryville, Alaska
  11. 2.4 122 km SE of Perryville, Alaska
  12. 2.8 108 km SE of Perryville, Alaska
  13. 2.5 120 km SE of Perryville, Alaska
  14. 2.4 139 km SSE of Perryville, Alaska
  15. 2.3 99 km SE of Chignik, 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.