QuakeIndex

Earthquake · reviewed by a seismologist

M 2.3ml

175 km SSE of Atka, Alaska

Yes. A magnitude 2.3 earthquake was recorded 175 km SSE of Atka, Alaska at 20:37 UTC on 2022-04-27, 28 km deep.

· 28 km deep · released about 85 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 2.3 (ml)
Depth
28 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 8 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 1611 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause 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 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
  3. Around the size people start to feel M 3.0 11× the energy of this one
  4. This earthquake M 2.3 about 85 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 4.2 on 2017-11-29 — about 710 times the energy of this one.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 182 km SSE of Atka, Alaska · 32 km ENE of this epicentre
  2. 5.8 174 km SSE of Atka, Alaska · 12 km ENE of this epicentre
  3. 5.8 161 km SSE of Atka, Alaska · 21 km NNE of this epicentre
  4. 5.8 165 km SSE of Atka, Alaska · 14 km NNE of this epicentre
  5. 5.8 150 km SSE of Atka, Alaska · 35 km NNE 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 50.7361, -173.2323. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.6 193 km SSE of Atka, Alaska
  2. 2.7 171 km SSE of Atka, Alaska
  3. 2.4 165 km S of Atka, Alaska
  4. 3.2 163 km SSE of Atka, Alaska
  5. 2.5 189 km SSE of Atka, Alaska
  6. 3.0 Andreanof Islands, Aleutian Islands, Alaska
  7. 2.9 149 km SSE of Atka, Alaska
  8. 3.0 Andreanof Islands, Aleutian Islands, Alaska
  9. 3.2 140 km SSE of Atka, Alaska
  10. 3.4 184 km SSE of Atka, Alaska
  11. 2.9 196 km SSE of Atka, Alaska
  12. 3.1 187 km SSE of Atka, Alaska
  13. 4.3 177 km SSE of Atka, Alaska
  14. 3.1 172 km S of Atka, Alaska
  15. 2.8 Andreanof Islands, Aleutian Islands, 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.