QuakeIndex

Earthquake · reviewed by a seismologist

M 1.5ml

18 km SW of Atka, Alaska

Yes. A magnitude 1.5 earthquake was recorded 18 km SW of Atka, Alaska at 13:42 UTC on 2025-09-11, 9.3 km deep.

· 9.3 km deep · released about 5.7 lb 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 1.5 (ml)
Depth
9.3 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 430 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 5 km (3 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 5.7 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,600,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,900,000× the energy of this one
  3. Around the size people start to feel M 3.0 170× the energy of this one
  4. This earthquake M 1.5 about 5.7 lb of TNT

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 5.3 on 2022-07-08 — about 470,000 times the energy of this one.

Before 2016, the USGS record lists 23 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.8 57 km SSW of Atka, Alaska · 44 km S of this epicentre
  2. 6.5 25 km NW of Atka, Alaska · 27 km NNW of this epicentre
  3. 6.4 37 km WNW of Atka, Alaska · 31 km NW of this epicentre
  4. 6.1 43 km S of Atka, Alaska · 34 km SSE of this epicentre
  5. 6.0 51 km SSE of Atka, Alaska · 48 km SE 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 52.0955, -174.4095. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.8 20 km SW of Atka, Alaska
  2. 2.8 45 km S of Atka, Alaska
  3. 2.6 48 km SSW of Atka, Alaska
  4. 1.9 41 km NNW of Atka, Alaska
  5. 1.9 32 km WSW of Atka, Alaska
  6. 3.3 24 km SSW of Atka, Alaska
  7. 2.3 53 km SW of Atka, Alaska
  8. 2.3 13 km NNW of Atka, Alaska
  9. 3.6 9 km NW of Atka, Alaska
  10. 2.0 34 km NNW of Atka, Alaska
  11. 2.4 44 km S of Atka, Alaska
  12. 2.3 36 km SSW of Atka, Alaska
  13. 3.3 52 km S of Atka, Alaska
  14. 1.7 12 km SE of Atka, Alaska
  15. 3.4 58 km SW of Atka, 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.