QuakeIndex

Earthquake · reviewed by a seismologist

M 3.8ml

157 km SE of Chignik, Alaska

· 5.6 km deep · released about 7.6 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 3.8 (ml)
Depth
5.6 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 1820 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

How big was it?

This earthquake released about 7.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 22,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 710× the energy of this one
  4. This earthquake M 3.8 about 7.6 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 16× 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 55.4513, -156.3801. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.5 123 km SE of Chignik, Alaska
  2. 4.4 166 km SE of Chignik, Alaska
  3. 2.5 168 km SE of Chignik, Alaska
  4. 2.4 147 km SE of Chignik, Alaska
  5. 3.6 154 km SE of Chignik, Alaska
  6. 2.8 171 km ESE of Chignik, Alaska
  7. 2.4 125 km SE of Chignik, Alaska
  8. 2.7 146 km SE of Chignik, Alaska
  9. 3.2 153 km SE of Chignik, Alaska
  10. 3.2 149 km SE of Chignik, Alaska
  11. 2.9 167 km SE of Chignik, Alaska
  12. 3.1 169 km ESE of Chignik, Alaska
  13. 3.9 153 km SE of Chignik, Alaska
  14. 5.4 158 km SE of Chignik, Alaska
  15. 5.0 142 km SE 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 5.4 on 2021-07-29 — 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.