QuakeIndex

Earthquake · reviewed by a seismologist

M 5.0mb

172 km ENE of Atka, Alaska

Yes. A magnitude 5.0 earthquake was recorded 172 km ENE of Atka, Alaska at 15:01 UTC on 2023-09-24, 109 km deep. 1 person has reported feeling it to USGS.

· 109 km deep · released about 480 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 5.0 (mb)
Depth
109 km below the surface
Felt
1 report · strongest reported intensity III
Measured shaking
intensity IV (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 432 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 160 km (99 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 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 350× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 16× the energy of this one
  3. Magna, Utah 2020 M 5.7 11× the energy of this one
  4. This earthquake M 5.0 about 480 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 1,000× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.8 on 2022-01-11.

Before 2016, the USGS record lists 10 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.8 167 km W of Nikolski, Alaska · 44 km NE of this epicentre
  2. 6.5 173 km ENE of Atka, Alaska · 44 km NNW of this epicentre
  3. 6.2 173 km WSW of Nikolski, Alaska · 27 km E of this epicentre
  4. 6.1 188 km E of Atka, Alaska · 47 km SSE of this epicentre
  5. 6.0 182 km E of Atka, Alaska · 43 km SSE 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 52.6283, -171.7732. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.7 172 km E of Atka, Alaska
  2. 3.4 169 km E of Atka, Alaska
  3. 3.5 165 km W of Nikolski, Alaska
  4. 2.9 177 km E of Atka, Alaska
  5. 3.9 179 km E of Atka, Alaska
  6. 2.9 179 km E of Atka, Alaska
  7. 3.5 176 km E of Atka, Alaska
  8. 2.9 177 km ENE of Atka, Alaska
  9. 2.8 176 km E of Atka, Alaska
  10. 3.9 170 km E of Atka, Alaska
  11. 4.4 171 km E of Atka, Alaska
  12. 3.0 173 km E of Atka, Alaska
  13. 4.4 167 km E of Atka, Alaska
  14. 3.5 178 km E of Atka, Alaska
  15. 5.6 172 km ENE 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.