QuakeIndex

Earthquake · reviewed by a seismologist

M 5.5mww

92 km S of Nikolski, Alaska

· 17 km deep · released about 2.7 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 5.5 (mww)
Depth
17 km below the surface
Felt
1 report · strongest reported intensity II
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 3 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 2.7 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 63× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2.8× the energy of this one
  3. Magna, Utah 2020 M 5.7 2× the energy of this one
  4. This earthquake M 5.5 about 2.7 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 5,600× 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 52.1060, -168.9557. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.3 59 km S of Nikolski, Alaska
  2. 2.3 55 km SSW of Nikolski, Alaska
  3. 2.5 87 km SSW of Nikolski, Alaska
  4. 2.6 102 km SSW of Nikolski, Alaska
  5. 2.2 63 km SSW of Nikolski, Alaska
  6. 2.4 86 km SSW of Nikolski, Alaska
  7. 2.5 99 km SSW of Nikolski, Alaska
  8. 3.0 70 km SSW of Nikolski, Alaska
  9. 2.3 77 km S of Nikolski, Alaska
  10. 2.5 76 km S of Nikolski, Alaska
  11. 2.6 53 km SSE of Nikolski, Alaska
  12. 2.5 64 km S of Nikolski, Alaska
  13. 2.7 85 km SSW of Nikolski, Alaska
  14. 2.5 61 km SSW of Nikolski, Alaska
  15. 2.3 52 km S 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 5.9 on 2025-09-03 — it released about 4 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.