QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

159 km SSW of Akhiok, Alaska

· 1.2 km deep · released about 15 lb 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 1.8 (ml)
Depth
1.2 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 330 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 15 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,000,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 710,000× the energy of this one
  3. Around the size people start to feel M 3.0 63× the energy of this one
  4. This earthquake M 1.8 about 15 lb of TNT

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 55.7283, -155.5429. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.4 168 km ESE of Chignik, Alaska
  2. 2.3 136 km SW of Akhiok, Alaska
  3. 2.7 183 km SSW of Akhiok, Alaska
  4. 3.0 183 km SSW of Akhiok, Alaska
  5. 2.3 160 km ESE of Chignik, Alaska
  6. 2.6 156 km SSW of Akhiok, Alaska
  7. 2.9 155 km SSW of Akhiok, Alaska
  8. 2.4 156 km SSW of Akhiok, Alaska
  9. 2.6 167 km ESE of Chignik, Alaska
  10. 3.1 150 km SW of Akhiok, Alaska
  11. 2.3 172 km SSW of Akhiok, Alaska
  12. 2.8 179 km SSW of Akhiok, Alaska
  13. 2.9 199 km SE of Chignik, Alaska
  14. 2.7 149 km SSW of Akhiok, Alaska
  15. 3.1 164 km ESE 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 4.8 on 2021-07-29 — it released about 32,000 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.