QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0ml

203 km SE of Perryville, Alaska

· 20 km deep · released about 15 tons 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 4.0 (ml)
Depth
20 km below the surface
Felt
no reports yet
Measured shaking
intensity I (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1611 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 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 11,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 500× the energy of this one
  3. Magna, Utah 2020 M 5.7 350× the energy of this one
  4. This earthquake M 4.0 about 15 tons of TNT
  5. Around the size people start to feel M 3.0 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 54.7005, -156.7352. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.4 197 km SE of Perryville, Alaska
  2. 4.0 189 km SE of Perryville, Alaska
  3. 2.3 225 km SE of Chignik, Alaska
  4. 2.8 219 km SE of Perryville, Alaska
  5. 2.7 208 km SE of Perryville, Alaska
  6. 2.6 206 km SE of Perryville, Alaska
  7. 2.3 176 km SE of Perryville, Alaska
  8. 2.6 198 km SE of Perryville, Alaska
  9. 3.1 198 km SE of Chignik, Alaska
  10. 2.6 203 km SE of Perryville, Alaska
  11. 2.4 208 km SE of Chignik, Alaska
  12. 2.5 163 km SE of Chignik, Alaska
  13. 2.6 196 km SE of Perryville, Alaska
  14. 2.4 224 km SE of Perryville, Alaska
  15. 2.8 205 km SE of Perryville, 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 5.6 on 2021-09-16 — it released about 250 times the energy of this one.

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

On USGS

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