QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1ml

south of Alaska

Yes. A magnitude 3.1 earthquake was recorded south of Alaska at 20:02 UTC on 2023-04-17, 25 km deep.

· 25 km deep · released about 1,300 lb of TNT

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10 km30 km60 km120 km N
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 3.1 (ml)
Depth
25 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1229 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 33 km (21 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 1,300 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 250,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 11,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 7,900× the energy of this one
  4. This earthquake M 3.1 about 1,300 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.4× 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 4.8 on 2022-08-17 — about 350 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. 6.9 143 km ESE of Chignik, Alaska · 39 km WSW of this epicentre
  2. 6.9 171 km SW of Akhiok, Alaska · 24 km SSW of this epicentre
  3. 6.2 148 km SSW of Akhiok, Alaska · 36 km ESE of this epicentre
  4. 6.1 132 km E of Chignik, Alaska · 48 km NW of this epicentre
  5. 6.0 108 km SSW of Akhiok, Alaska · 49 km ENE 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 55.9153, -155.6900. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.6 146 km SW of Akhiok, Alaska
  2. 1.8 149 km ESE of Chignik, Alaska
  3. 1.8 159 km ESE of Chignik, Alaska
  4. 3.0 147 km SW of Akhiok, Alaska
  5. 2.4 156 km SSW of Akhiok, Alaska
  6. 3.1 153 km SSW of Akhiok, Alaska
  7. 1.8 118 km SW of Akhiok, Alaska
  8. 3.3 165 km ESE of Chignik, Alaska
  9. 2.5 149 km SW of Akhiok, Alaska
  10. 2.4 155 km SSW of Akhiok, Alaska
  11. 1.9 113 km SW of Akhiok, Alaska
  12. 2.8 150 km SSW of Akhiok, Alaska
  13. 2.6 152 km ESE of Chignik, Alaska
  14. 3.9 174 km ESE of Chignik, Alaska
  15. 2.3 162 km SSW of Akhiok, 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.