QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

127 km E of Chignik, Alaska

· 29 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
29 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1123 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 56.3999, -156.3556. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.6 108 km E of Chignik, Alaska
  2. 1.9 104 km SSE of Ugashik, Alaska
  3. 2.6 149 km SW of Akhiok, Alaska
  4. 2.5 103 km ENE of Chignik, Alaska
  5. 2.3 119 km ENE of Chignik, Alaska
  6. 2.1 114 km SSE of Ugashik, Alaska
  7. 2.3 117 km SSE of Ugashik, Alaska
  8. 1.8 103 km ENE of Chignik, Alaska
  9. 1.8 101 km ENE of Chignik, Alaska
  10. 2.4 96 km E of Chignik, Alaska
  11. 2.2 112 km E of Chignik, Alaska
  12. 2.5 119 km SSE of Ugashik, Alaska
  13. 1.9 116 km WSW of Akhiok, Alaska
  14. 2.5 108 km E of Chignik, Alaska
  15. 2.5 115 km WSW 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 6.9 on 2021-10-11 — it released about 45,000,000 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.