QuakeIndex

Earthquake · reviewed by a seismologist

M 4.1mb

180 km SSE of Atka, Alaska

Yes. A magnitude 4.1 earthquake was recorded 180 km SSE of Atka, Alaska at 04:19 UTC on 2020-10-06, 24 km deep.

· 24 km deep · released about 21 tons 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 4.1 (mb)
Depth
24 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 12 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 2162 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 102 km (63 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 21 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 7,900× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 350× the energy of this one
  3. Magna, Utah 2020 M 5.7 250× the energy of this one
  4. This earthquake M 4.1 about 21 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 45× more

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 4.5 on 2017-01-10 — about 4 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 · 30 km ENE of this epicentre
  2. 5.8 174 km SSE of Atka, Alaska · 13 km NNE of this epicentre
  3. 5.8 161 km SSE of Atka, Alaska · 24 km N of this epicentre
  4. 5.8 165 km SSE of Atka, Alaska · 17 km N of this epicentre
  5. 5.8 150 km SSE of Atka, Alaska · 38 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 50.6992, -173.1827. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.2 221 km SSE of Atka, Alaska
  2. 2.1 208 km SSE of Atka, Alaska
  3. 2.3 216 km SSE of Atka, Alaska
  4. 2.8 190 km SSE of Atka, Alaska
  5. 2.3 186 km SSE of Atka, Alaska
  6. 3.1 185 km SSE of Atka, Alaska
  7. 2.3 175 km SSE of Atka, Alaska
  8. 2.8 160 km SSE of Atka, Alaska
  9. 2.7 144 km SSE of Atka, Alaska
  10. 3.8 161 km SSE of Atka, Alaska
  11. 2.5 146 km SSE of Atka, Alaska
  12. 2.3 176 km SSE of Atka, Alaska
  13. 3.2 194 km SSE of Atka, Alaska
  14. 2.7 175 km SSE of Atka, Alaska
  15. 2.9 183 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.