QuakeIndex

Earthquake · reviewed by a seismologist

M 4.5ml

151 km SSW of Akhiok, Alaska

· 8.5 km deep · released about 85 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 4.5 (ml)
Depth
8.5 km below the surface
Felt
2 reports · strongest reported intensity II
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1709 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon. 2 people have reported feeling it to USGS.

How big was it?

This earthquake released about 85 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 2,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 89× the energy of this one
  3. Magna, Utah 2020 M 5.7 63× the energy of this one
  4. This earthquake M 4.5 about 85 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 180× 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 55.8034, -155.5144. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.2 152 km SSW of Akhiok, Alaska
  2. 2.5 165 km ESE of Chignik, Alaska
  3. 2.5 155 km SW of Akhiok, Alaska
  4. 4.0 152 km SSW of Akhiok, Alaska
  5. 2.2 south of Alaska
  6. 3.5 157 km SSW of Akhiok, Alaska
  7. 2.3 153 km ESE of Chignik, Alaska
  8. 3.4 166 km SSW of Akhiok, Alaska
  9. 2.4 154 km SSW of Akhiok, Alaska
  10. 2.9 150 km ESE of Chignik, Alaska
  11. 3.1 134 km SSW of Akhiok, Alaska
  12. 1.9 114 km SW of Akhiok, Alaska
  13. 3.0 158 km SW of Akhiok, Alaska
  14. 2.3 143 km SW of Akhiok, Alaska
  15. 3.0 193 km SSW of Akhiok, 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 4.8 on 2021-07-29 — it released about 2.8 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.