QuakeIndex

Earthquake · reviewed by a seismologist

M 5.2mww

126 km S of Unalaska, Alaska

Yes. A magnitude 5.2 earthquake was recorded 126 km S of Unalaska, Alaska, at 2:55 am AKST on 21 January 2025 (11:55 UTC), 10 km deep. 2 people have reported feeling it to USGS.

· 10 km deep · released about 950 tons of TNT

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10 km30 km60 km120 km N
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 5.2 (mww)
Depth
10 km below the surface
Felt
2 reports · strongest reported intensity III
Measured shaking
intensity III (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 119 days ago

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

At this magnitude and depth, people at rest would likely notice it out to about 218 km (135 mi) from the epicentre. Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

How big was it?

This earthquake released about 950 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.2 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 180× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 7.9× the energy of this one
  3. Magna, Utah 2020 M 5.7 5.6× the energy of this one
  4. This earthquake M 5.2 about 950 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 2,000× 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.

For this area

The largest earthquake within 50 km since 2016 was M 5.9 on 2017-05-24 — about 11 times the energy of this one.

Before 2016, the USGS record lists 42 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 127 km E of Nikolski, Alaska · 23 km W of this epicentre
  2. 6.4 118 km E of Nikolski, Alaska · 32 km W of this epicentre
  3. 6.4 123 km ESE of Nikolski, Alaska · 35 km WSW of this epicentre
  4. 6.3 136 km ESE of Nikolski, Alaska · 21 km WSW of this epicentre
  5. 6.3 Fox Islands, Aleutian Islands, Alaska · 41 km WSW of this epicentre

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 52.7426, -166.6507. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.1 125 km S of Unalaska, Alaska
  2. 1.9 111 km S of Unalaska, Alaska
  3. 2.9 129 km S of Unalaska, Alaska
  4. 2.1 109 km S of Unalaska, Alaska
  5. 2.0 119 km S of Unalaska, Alaska
  6. 2.2 127 km ESE of Nikolski, Alaska
  7. 2.6 143 km ESE of Nikolski, Alaska
  8. 2.5 132 km S of Unalaska, Alaska
  9. 1.9 98 km SSW of Unalaska, Alaska
  10. 2.1 78 km SSW of Unalaska, Alaska
  11. 2.7 117 km S of Unalaska, Alaska
  12. 2.2 139 km S of Unalaska, Alaska
  13. 2.2 129 km SSW of Unalaska, Alaska
  14. 2.2 133 km S of Unalaska, Alaska
  15. 2.0 135 km S of Unalaska, 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.

On USGS

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