QuakeIndex

Earthquake · reviewed by a seismologist

M 5.4mww

142 km WSW of Adak, Alaska

· 45 km deep · released about 1.9 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 5.4 (mww)
Depth
45 km below the surface
Felt
5 reports · strongest reported intensity III
Measured shaking
intensity III (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 21 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre. 5 people have reported feeling it to USGS.

How big was it?

This earthquake released about 1.9 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 89× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 4× the energy of this one
  3. Magna, Utah 2020 M 5.7 2.8× the energy of this one
  4. This earthquake M 5.4 about 1.9 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 4,000× 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 51.2868, -178.4612. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.9 139 km W of Adak, Alaska
  2. 2.7 140 km SW of Adak, Alaska
  3. 2.4 143 km SW of Adak, Alaska
  4. 1.9 116 km WSW of Adak, Alaska
  5. 2.2 161 km WSW of Adak, Alaska
  6. 2.0 178 km WSW of Adak, Alaska
  7. 2.2 114 km WSW of Adak, Alaska
  8. 1.9 114 km WSW of Adak, Alaska
  9. 3.2 119 km WSW of Adak, Alaska
  10. 4.2 114 km WSW of Adak, Alaska
  11. 2.1 176 km WSW of Adak, Alaska
  12. 3.8 113 km WSW of Adak, Alaska
  13. 1.9 122 km SW of Adak, Alaska
  14. 2.1 150 km WSW of Adak, Alaska
  15. 2.1 134 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 6.5 on 2018-08-15 — it released about 45 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.