QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9mb

156 km WSW of Adak, Alaska

· 35 km deep · released about 11 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 3.9 (mb)
Depth
35 km below the surface
Felt
no reports yet
Measured shaking
intensity I (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 458 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

How big was it?

This earthquake released about 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
  3. Magna, Utah 2020 M 5.7 500× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× 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 51.1958, -178.6153. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.0 154 km WSW of Adak, Alaska
  2. 2.1 129 km WSW of Adak, Alaska
  3. 1.9 136 km WSW of Adak, Alaska
  4. 2.7 178 km WSW of Adak, Alaska
  5. 1.9 127 km WSW of Adak, Alaska
  6. 1.6 152 km WSW of Adak, Alaska
  7. 1.7 152 km WSW of Adak, Alaska
  8. 1.7 118 km WSW of Adak, Alaska
  9. 2.0 186 km WSW of Adak, Alaska
  10. 2.5 182 km WSW of Adak, Alaska
  11. 1.6 139 km WSW of Adak, Alaska
  12. 1.7 142 km WSW of Adak, Alaska
  13. 1.7 171 km WSW of Adak, Alaska
  14. 1.6 141 km WSW of Adak, Alaska
  15. 1.6 133 km SW of Adak, 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 6.1 on 2021-09-24 — it released about 2,000 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.