QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0mb

184 km SSE of Atka, Alaska

Yes. A magnitude 4.0 earthquake was recorded 184 km SSE of Atka, Alaska at 16:42 UTC on 2018-01-13, 22 km deep.

· 22 km deep · released about 15 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 4.0 (mb)
Depth
22 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 17 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 1191 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 94 km (58 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 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 11,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 500× the energy of this one
  3. Magna, Utah 2020 M 5.7 350× the energy of this one
  4. This earthquake M 4.0 about 15 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 32× 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 5.6 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 · 37 km ENE of this epicentre
  2. 5.8 174 km SSE of Atka, Alaska · 20 km NE of this epicentre
  3. 5.8 161 km SSE of Atka, Alaska · 31 km NNE of this epicentre
  4. 5.8 165 km SSE of Atka, Alaska · 24 km NNE of this epicentre
  5. 5.8 150 km SSE of Atka, Alaska · 45 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 50.6458, -173.2526. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.4 175 km SSE of Atka, Alaska
  2. 2.7 205 km SSE of Atka, Alaska
  3. 2.5 167 km SSE of Atka, Alaska
  4. 3.3 167 km SSE of Atka, Alaska
  5. 2.6 142 km SSE of Atka, Alaska
  6. 2.8 163 km SSE of Atka, Alaska
  7. 2.7 155 km SSE of Atka, Alaska
  8. 2.7 184 km S of Atka, Alaska
  9. 3.3 204 km SSE of Atka, Alaska
  10. 2.2 172 km SSE of Atka, Alaska
  11. 2.9 157 km SSE of Atka, Alaska
  12. 3.9 200 km SSE of Atka, Alaska
  13. 3.8 193 km SSE of Atka, Alaska
  14. 2.5 Andreanof Islands, Aleutian Islands, Alaska
  15. 2.5 153 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.