QuakeIndex

Earthquake · reviewed by a seismologist

M 5.6mww

209 km WSW of Adak, Alaska

· 19 km deep · released about 3.8 kilotons 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 5.6 (mww)
Depth
19 km below the surface
Felt
no reports yet
Measured shaking
intensity V (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 279 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

How big was it?

This earthquake released about 3.8 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.6 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 45× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2× the energy of this one
  3. Magna, Utah 2020 M 5.7 1.4× the energy of this one
  4. This earthquake M 5.6 about 3.8 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 7,900× 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 50.9446, -179.2536. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.7 199 km WSW of Adak, Alaska
  2. 1.7 176 km WSW of Adak, Alaska
  3. 1.6 206 km WSW of Adak, Alaska
  4. 3.9 220 km WSW of Adak, Alaska
  5. 1.8 183 km WSW of Adak, Alaska
  6. 1.7 197 km WSW of Adak, Alaska
  7. 2.0 186 km WSW of Adak, Alaska
  8. 1.9 Andreanof Islands, Aleutian Islands, Alaska
  9. 2.0 197 km WSW of Adak, Alaska
  10. 2.9 203 km WSW of Adak, Alaska
  11. 2.1 196 km WSW of Adak, Alaska
  12. 2.0 194 km WSW of Adak, Alaska
  13. 2.1 184 km WSW of Adak, Alaska
  14. 3.4 202 km WSW of Adak, Alaska
  15. 2.0 181 km WSW 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 2021-01-03 — it released about 5.6 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.