QuakeIndex

Earthquake · reviewed by a seismologist

M 3.0ml

171 km SSE of Atka, Alaska

Yes. A magnitude 3.0 earthquake was recorded 171 km SSE of Atka, Alaska at 14:39 UTC on 2021-08-05, 17 km deep.

· 17 km deep · released about 950 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 3.0 (ml)
Depth
17 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 1 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 1857 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 32 km (20 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 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 350,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 16,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 11,000× the energy of this one
  4. This earthquake M 3.0 about 950 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 63 times the energy of this one.

Before 2016, the USGS record lists 12 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 182 km SSE of Atka, Alaska · 26 km E of this epicentre
  2. 5.8 174 km SSE of Atka, Alaska · 5 km E of this epicentre
  3. 5.8 161 km SSE of Atka, Alaska · 13 km NNE of this epicentre
  4. 5.8 165 km SSE of Atka, Alaska · 6 km N of this epicentre
  5. 5.8 150 km SSE of Atka, Alaska · 26 km N 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 50.8023, -173.1591. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.3 Andreanof Islands, Aleutian Islands, Alaska
  2. 2.8 185 km SSE of Atka, Alaska
  3. 3.9 189 km SSE of Atka, Alaska
  4. 3.2 198 km SSE of Atka, Alaska
  5. 2.6 205 km SSE of Atka, Alaska
  6. 2.9 173 km SSE of Atka, Alaska
  7. 2.6 131 km SSE of Atka, Alaska
  8. 3.0 202 km SSE of Atka, Alaska
  9. 2.3 157 km SSE of Atka, Alaska
  10. 2.9 186 km SSE of Atka, Alaska
  11. 2.2 168 km SSE of Atka, Alaska
  12. 2.9 199 km SSE of Atka, Alaska
  13. 3.0 159 km SSE of Atka, Alaska
  14. 1.9 162 km SSE of Atka, Alaska
  15. 3.1 186 km SSE 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.