QuakeIndex

Earthquake · reviewed by a seismologist

M 5.6mww

122 km ESE of Nikolski, Alaska

· 13 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
13 km below the surface
Felt
2 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 319 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre. 2 people have reported feeling it to USGS.

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 52.7331, -167.0686. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.1 83 km SSW of Unalaska, Alaska
  2. 2.0 134 km ESE of Nikolski, Alaska
  3. 2.0 142 km ESE of Nikolski, Alaska
  4. 2.3 139 km ESE of Nikolski, Alaska
  5. 1.9 90 km ESE of Nikolski, Alaska
  6. 1.7 97 km E of Nikolski, Alaska
  7. 3.6 135 km ESE of Nikolski, Alaska
  8. 2.8 135 km ESE of Nikolski, Alaska
  9. 2.0 94 km SSW of Unalaska, Alaska
  10. 2.6 134 km ESE of Nikolski, Alaska
  11. 2.1 115 km ESE of Nikolski, Alaska
  12. 3.4 92 km E of Nikolski, Alaska
  13. 3.2 151 km ESE of Nikolski, Alaska
  14. 3.9 118 km E of Nikolski, Alaska
  15. 1.8 87 km E of Nikolski, 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 5.5 on 2019-07-09.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.