QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9ml

201 km SE of Chignik, Alaska

· 4.1 km deep · released about 11 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 3.9 (ml)
Depth
4.1 km below the surface
Felt
1 report · strongest reported intensity I
Measured shaking
intensity II (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1744 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
  3. Magna, Utah 2020 M 5.7 500× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× 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 54.9128, -156.2256. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.9 218 km SE of Chignik, Alaska
  2. 3.2 210 km SE of Perryville, Alaska
  3. 2.8 191 km SE of Chignik, Alaska
  4. 2.8 206 km SE of Chignik, Alaska
  5. 2.0 188 km SE of Chignik, Alaska
  6. 2.6 190 km SE of Chignik, Alaska
  7. 3.0 192 km SE of Chignik, Alaska
  8. 2.8 south of Alaska
  9. 2.7 195 km SE of Chignik, Alaska
  10. 2.6 192 km SE of Chignik, Alaska
  11. 2.9 216 km SE of Chignik, Alaska
  12. 3.1 204 km SE of Perryville, Alaska
  13. 2.3 225 km SE of Chignik, Alaska
  14. 2.6 206 km SE of Perryville, Alaska
  15. 3.1 198 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 5.6 on 2021-09-16 — it released about 350 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.