QuakeIndex

Earthquake · reviewed by a seismologist

M 4.7ml

128 km SSE of Perryville, Alaska

· 2.5 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
2.5 km below the surface
Felt
no reports yet
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1821 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 54.9511, -158.0184. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.3 114 km SSE of Perryville, Alaska
  2. 2.6 104 km SSE of Perryville, Alaska
  3. 2.5 119 km SE of Perryville, Alaska
  4. 1.9 120 km SE of Perryville, Alaska
  5. 3.7 139 km SE of Perryville, Alaska
  6. 2.3 143 km SE of Perryville, Alaska
  7. 3.1 137 km SE of Perryville, Alaska
  8. 2.6 134 km SE of Perryville, Alaska
  9. 2.8 Alaska Peninsula
  10. 2.5 116 km SE of Perryville, Alaska
  11. 2.5 141 km SE of Perryville, Alaska
  12. 2.7 129 km SSE of Perryville, Alaska
  13. 2.8 141 km SSE of Perryville, Alaska
  14. 2.7 126 km SSE of Perryville, Alaska
  15. 2.1 123 km SSE 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.