QuakeIndex

Earthquake · reviewed by a seismologist

M 5.8mww

82 km ESE of Adak, Alaska

· 34 km deep · released about 7.6 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 5.8 (mww)
Depth
34 km below the surface
Felt
4 reports · strongest reported intensity III
Measured shaking
intensity IV (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 72 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre. 4 people have reported feeling it to USGS.

How big was it?

This earthquake released about 7.6 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.8 would have released about 32 times as much.

  1. Ridgecrest, California 2019 M 7.1 89× the energy of this one
  2. Loma Prieta, California 1989 M 6.9 45× the energy of this one
  3. Northridge, California 1994 M 6.7 22× the energy of this one
  4. This earthquake M 5.8 about 7.6 kilotons of TNT
  5. Magna, Utah 2020 M 5.7 this one released 1.4× more
  6. Around the size people start to feel M 3.0 this one released 16,000× 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 51.4799, -175.6197. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.8 83 km ESE of Adak, Alaska
  2. 2.2 60 km ESE of Adak, Alaska
  3. 1.9 93 km SW of Atka, Alaska
  4. 1.7 84 km SE of Adak, Alaska
  5. 3.2 92 km SE of Adak, Alaska
  6. 1.9 85 km ESE of Adak, Alaska
  7. 3.4 91 km SE of Adak, Alaska
  8. 1.8 76 km SE of Adak, Alaska
  9. 1.6 77 km SE of Adak, Alaska
  10. 1.7 75 km SE of Adak, Alaska
  11. 1.6 73 km SE of Adak, Alaska
  12. 1.9 83 km SE of Adak, Alaska
  13. 3.4 90 km SE of Adak, Alaska
  14. 2.2 58 km SSE of Adak, Alaska
  15. 1.6 78 km SE 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 6.3 on 2019-11-24 — 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.