QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0ml

136 km SSE of Chignik, Alaska

· 24 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
24 km below the surface
Felt
no reports yet
Measured shaking
intensity I (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1810 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 55.2446, -157.2797. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.2 154 km SSE of Chignik, Alaska
  2. 2.9 145 km SE of Perryville, Alaska
  3. 3.7 152 km SSE of Chignik, Alaska
  4. 2.5 112 km SE of Chignik, Alaska
  5. 3.3 133 km SE of Perryville, Alaska
  6. 3.2 144 km SSE of Chignik, Alaska
  7. 3.1 146 km SE of Perryville, Alaska
  8. 3.2 137 km SE of Perryville, Alaska
  9. 2.3 140 km SE of Chignik, Alaska
  10. 2.3 127 km SE of Perryville, Alaska
  11. 2.3 143 km SE of Perryville, Alaska
  12. 2.1 145 km SE of Perryville, Alaska
  13. 2.4 142 km SE of Chignik, Alaska
  14. 3.3 156 km SE of Chignik, Alaska
  15. 3.5 155 km SSE 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.

For this area

The largest earthquake within 50 km in our catalogue was M 5.9 on 2021-07-29 — it released about 710 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.