QuakeIndex

Earthquake · reviewed by a seismologist

M 4.5mb

south of Alaska

Yes. A magnitude 4.5 earthquake was recorded south of Alaska at 18:18 UTC on 2022-08-30, 5.0 km deep. 1 person has reported feeling it to USGS.

· 5.0 km deep · released about 85 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 4.5 (mb)
Depth
5.0 km below the surface
Felt
1 report · strongest reported intensity II
Measured shaking
intensity II (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1468 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 139 km (86 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 85 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 2,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 89× the energy of this one
  3. Magna, Utah 2020 M 5.7 63× the energy of this one
  4. This earthquake M 4.5 about 85 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 180× 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 2021-07-29 — about 2.8 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 6.1 210 km SE of Chignik, Alaska · 16 km NW of this epicentre
  2. 6.0 223 km SSW of Akhiok, Alaska · 3 km N of this epicentre
  3. 5.8 188 km SSW of Akhiok, Alaska · 50 km NNW of this epicentre
  4. 5.6 205 km SE of Chignik, Alaska · 48 km WSW 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 55.0609, -155.5416. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.4 209 km SSW of Akhiok, Alaska
  2. 2.7 183 km SSW of Akhiok, Alaska
  3. 2.9 204 km SSW of Akhiok, Alaska
  4. 3.0 256 km SE of Chignik, Alaska
  5. 2.9 199 km SE of Chignik, Alaska
  6. 3.4 208 km SE of Chignik, Alaska
  7. 2.8 215 km SE of Chignik, Alaska
  8. 3.0 178 km SE of Chignik, Alaska
  9. 2.7 186 km ESE of Chignik, Alaska
  10. 2.2 217 km SE of Chignik, Alaska
  11. 4.6 208 km SSW of Akhiok, Alaska
  12. 2.9 190 km SSW of Akhiok, Alaska
  13. 2.9 190 km SE of Chignik, Alaska
  14. 3.5 205 km SE of Chignik, Alaska
  15. 3.3 192 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.