QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0ml

17 km W of Chignik Lake, Alaska

· 9.5 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
9.5 km below the surface
Felt
1 report · strongest reported intensity III
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2247 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon. 1 person has reported feeling it to USGS.

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 56.2854, -159.0343. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.2 3 km SW of Chignik Lagoon, Alaska
  2. 2.6 53 km WNW of Chignik Lake, Alaska
  3. 2.7 Alaska Peninsula
  4. 1.7 26 km E of Perryville, Alaska
  5. 1.5 27 km W of Chignik Lake, Alaska
  6. 2.1 22 km N of Ivanof Bay, Alaska
  7. 1.9 20 km WNW of Chignik Lake, Alaska
  8. 1.9 21 km N of Chignik Lagoon, Alaska
  9. 1.6 1 km SSW of Perryville, Alaska
  10. 3.3 25 km W of Chignik Lake, Alaska
  11. 1.8 17 km NNE of Ivanof Bay, Alaska
  12. 1.9 40 km W of Chignik Lake, Alaska
  13. 3.7 15 km NW of Chignik Lake, Alaska
  14. 1.8 31 km N of Chignik Lake, Alaska
  15. 2.6 20 km N 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.

On USGS

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