QuakeIndex

Earthquake · reviewed by a seismologist

M 5.1mww

200 km SE of Chignik, Alaska

· 33 km deep · released about 670 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 5.1 (mww)
Depth
33 km below the surface
Felt
1 report · strongest reported intensity II
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 279 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 670 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 250× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 11× the energy of this one
  3. Magna, Utah 2020 M 5.7 7.9× the energy of this one
  4. This earthquake M 5.1 about 670 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 1,400× 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 54.9420, -156.3037. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.8 231 km SE of Chignik, Alaska
  2. 2.5 220 km SE of Chignik, Alaska
  3. 2.6 244 km SE of Chignik, Alaska
  4. 2.7 206 km SE of Chignik, Alaska
  5. 3.0 239 km SE of Chignik, Alaska
  6. 2.3 216 km SE of Perryville, Alaska
  7. 2.8 201 km SE of Perryville, Alaska
  8. 4.4 209 km SE of Perryville, Alaska
  9. 2.5 170 km SE of Chignik, Alaska
  10. 2.8 208 km SE of Perryville, Alaska
  11. 2.5 204 km SE of Perryville, Alaska
  12. 2.5 212 km SE of Chignik, Alaska
  13. 4.2 223 km SE of Chignik, Alaska
  14. 2.6 187 km SE of Chignik, Alaska
  15. 3.0 190 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 5.6 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.