QuakeIndex

Earthquake · reviewed by a seismologist

M 5.2mwr

148 km WSW of Adak, Alaska

Yes. A magnitude 5.2 earthquake was recorded 148 km WSW of Adak, Alaska at 03:49 UTC on 2025-04-16, 35 km deep. 3 people have reported feeling it to USGS.

· 35 km deep · released about 950 tons 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 5.2 (mwr)
Depth
35 km below the surface
Felt
3 reports · strongest reported intensity III
Measured shaking
intensity II (ShakeMap)
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 506 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 216 km (134 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 6.5 on 2018-08-15 — about 89 times the energy of this one.

Before 2016, the USGS record lists 233 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 162 km WSW of Adak, Alaska · 37 km NW of this epicentre
  2. 7.0 114 km WSW of Adak, Alaska · 37 km NE of this epicentre
  3. 7.0 148 km WSW of Adak, Alaska · 18 km NNW of this epicentre
  4. 6.9 151 km WSW of Adak, Alaska · 24 km NW of this epicentre
  5. 6.8 111 km SW of Adak, Alaska · 39 km ENE 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 51.1962, -178.4701. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.6 141 km WSW of Adak, Alaska
  2. 1.6 133 km SW of Adak, Alaska
  3. 2.1 126 km WSW of Adak, Alaska
  4. 2.9 140 km SW of Adak, Alaska
  5. 2.1 130 km WSW of Adak, Alaska
  6. 3.0 123 km SW of Adak, Alaska
  7. 2.2 145 km WSW of Adak, Alaska
  8. 2.9 144 km WSW of Adak, Alaska
  9. 2.2 147 km WSW of Adak, Alaska
  10. 1.9 141 km WSW of Adak, Alaska
  11. 1.7 129 km WSW of Adak, Alaska
  12. 3.3 122 km WSW of Adak, Alaska
  13. 1.9 119 km WSW of Adak, Alaska
  14. 1.9 147 km WSW of Adak, Alaska
  15. 2.2 150 km WSW 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.

On USGS

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