QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8ml

174 km S of Atka, Alaska

Yes. A magnitude 2.8 earthquake was recorded 174 km S of Atka, Alaska at 20:51 UTC on 2024-09-27, 10 km deep.

· 10 km deep · released about 480 lb 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 2.8 (ml)
Depth
10 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 6 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 708 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, people at rest would likely notice it out to about 25 km (16 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 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
  3. Around the size people start to feel M 3.0 2× the energy of this one
  4. This earthquake M 2.8 about 480 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 500 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 6.6 208 km S of Atka, Alaska · 34 km S of this epicentre
  2. 6.1 193 km SE of Adak, Alaska · 47 km WSW of this epicentre
  3. 5.8 131 km S of Atka, Alaska · 43 km N of this epicentre
  4. 5.6 178 km SE of Adak, Alaska · 49 km W of this epicentre
  5. 5.6 185 km S of Atka, Alaska · 22 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 50.6331, -174.2908. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.9 167 km S of Atka, Alaska
  2. 2.9 151 km S of Atka, Alaska
  3. 3.3 170 km S of Atka, Alaska
  4. 2.8 203 km S of Atka, Alaska
  5. 3.0 195 km S of Atka, Alaska
  6. 2.8 149 km S of Atka, Alaska
  7. 2.7 128 km S of Atka, Alaska
  8. 3.3 201 km S of Atka, Alaska
  9. 2.9 210 km S of Atka, Alaska
  10. 2.9 154 km S of Atka, Alaska
  11. 2.6 171 km S of Atka, Alaska
  12. 2.3 149 km S of Atka, Alaska
  13. 2.5 167 km S of Atka, Alaska
  14. 1.8 134 km S of Atka, Alaska
  15. 2.5 174 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.