QuakeIndex

Earthquake · reviewed by a seismologist

M 4.7ml

128 km SSE of Chignik, Alaska

· 26 km deep · released about 170 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 4.7 (ml)
Depth
26 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 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 170 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.7 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 1,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 45× the energy of this one
  3. Magna, Utah 2020 M 5.7 32× the energy of this one
  4. This earthquake M 4.7 about 170 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 350× 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 55.2815, -157.4372. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.0 138 km SE of Chignik, Alaska
  2. 2.6 128 km SE of Perryville, Alaska
  3. 3.1 155 km SSE of Chignik, Alaska
  4. 2.4 136 km SE of Chignik, Alaska
  5. 3.2 113 km ESE of Perryville, Alaska
  6. 2.5 125 km SE of Chignik, Alaska
  7. 2.6 157 km SSE of Chignik, Alaska
  8. 5.3 155 km SE of Chignik, Alaska
  9. 2.7 139 km SE of Perryville, Alaska
  10. 2.5 144 km SSE of Chignik, Alaska
  11. 2.6 133 km SE of Chignik, Alaska
  12. 2.7 143 km SE of Chignik, Alaska
  13. 3.1 148 km SE of Perryville, Alaska
  14. 3.0 Alaska Peninsula
  15. 2.8 149 km SE 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.

For this area

The largest earthquake within 50 km in our catalogue was M 8.2 on 2021-07-29 — it released about 180,000 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.