QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5ml

174 km S of Atka, Alaska

Yes. A magnitude 2.5 earthquake was recorded 174 km S of Atka, Alaska at 06:56 UTC on 2025-08-16, 25 km deep.

· 25 km deep · released about 170 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 2.5 (ml)
Depth
25 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 9 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 380 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. 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 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
  3. Around the size people start to feel M 3.0 5.6× the energy of this one
  4. This earthquake M 2.5 about 170 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 4.6 on 2023-04-22 — about 1,400 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 6.6 208 km S of Atka, Alaska · 36 km SSW of this epicentre
  2. 5.8 131 km S of Atka, Alaska · 47 km NNW of this epicentre
  3. 5.6 185 km S of Atka, Alaska · 32 km WSW of this epicentre
  4. 5.4 198 km SSE of Atka, Alaska · 44 km ESE 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 50.6259, -174.1389. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.9 186 km S of Atka, Alaska
  2. 2.9 210 km S of Atka, Alaska
  3. 2.6 158 km S of Atka, Alaska
  4. 2.6 158 km S of Atka, Alaska
  5. 3.1 153 km S of Atka, Alaska
  6. 2.6 147 km SSE of Atka, Alaska
  7. 2.5 170 km S of Atka, Alaska
  8. 2.6 191 km S of Atka, Alaska
  9. 2.4 182 km S of Atka, Alaska
  10. 3.1 195 km S of Atka, Alaska
  11. 2.7 137 km SSE of Atka, Alaska
  12. 2.8 154 km S of Atka, Alaska
  13. 2.8 162 km SSE of Atka, Alaska
  14. 3.1 141 km S of Atka, Alaska
  15. 2.6 213 km S 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.