QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0mb

22 km NNE of Larsen Bay, Alaska

· 45 km deep · released about 15 tons of TNT

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10 km30 km60 km120 km N Kodiak Island Borough 4 km
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
45 km below the surface
Felt
no reports yet
Measured shaking
intensity II (ShakeMap)
Nearest
Kodiak Island Borough, 4 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1463 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 57.7356, -153.8987. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Kodiak Island Borough, AK 4 km (2 mi) NNE of here earthquakes near Kodiak Island Borough

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

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

  1. 2.0 27 km W of Aleneva, Alaska
  2. 1.5 7 km NNE of Karluk, Alaska
  3. 1.7 15 km NW of Larsen Bay, Alaska
  4. 1.8 Kodiak Island region, Alaska
  5. 1.9 42 km N of Larsen Bay, Alaska
  6. 2.1 42 km W of Port Lions, Alaska
  7. 1.6 8 km WNW of Larsen Bay, Alaska
  8. 1.9 46 km W of Aleneva, Alaska
  9. 1.8 Kodiak Island region, Alaska
  10. 1.6 Kodiak Island region, Alaska
  11. 2.7 57 km NNE of Karluk, Alaska
  12. 2.0 38 km NNE of Larsen Bay, Alaska
  13. 2.8 20 km SE of Karluk, Alaska
  14. 1.5 16 km ESE of Larsen Bay, Alaska
  15. 1.5 48 km N of Larsen Bay, 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 4.9 on 2021-01-03 — it released about 22 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.