QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0mb

234 km SW of Nikolski, Alaska

· 10 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 (mb)
Depth
10 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1632 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 51.2464, -170.9081. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.0 243 km SSW of Nikolski, Alaska
  2. 3.1 265 km SE of Atka, Alaska
  3. 3.7 196 km SW of Nikolski, Alaska
  4. 3.5 217 km ESE of Atka, Alaska
  5. 3.7 228 km SW of Nikolski, Alaska
  6. 3.2 217 km SSW of Nikolski, Alaska
  7. 2.8 216 km SW of Nikolski, Alaska
  8. 2.8 270 km SSW of Nikolski, Alaska
  9. 3.8 229 km SW of Nikolski, Alaska
  10. 3.7 234 km SW of Nikolski, Alaska
  11. 2.5 238 km ESE of Atka, Alaska
  12. 3.9 217 km SSW of Nikolski, Alaska
  13. 2.9 248 km ESE of Atka, Alaska
  14. 2.3 213 km SW of Nikolski, Alaska
  15. 3.1 215 km ESE of Atka, 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 5.8 on 2020-08-16 — it released about 500 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.