QuakeIndex

Earthquake · reviewed by a seismologist

M 3.6ml

192 km SSW of Akhiok, Alaska

Yes. A magnitude 3.6 earthquake was recorded 192 km SSW of Akhiok, Alaska at 08:30 UTC on 2021-08-09, 37 km deep.

· 37 km deep · released about 3.8 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 3.6 (ml)
Depth
37 km below the surface
Felt
no reports yet
Measured shaking
intensity I (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1847 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 59 km (37 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 3.8 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.6 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 45,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 1,400× the energy of this one
  4. This earthquake M 3.6 about 3.8 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 7.9× 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 63 times the energy of this one.

Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.0 164 km SE of Chignik, Alaska · 49 km WSW of this epicentre
  2. 6.9 171 km SW of Akhiok, Alaska · 34 km NNW of this epicentre
  3. 6.2 148 km SSW of Akhiok, Alaska · 45 km NE of this epicentre
  4. 6.1 210 km SE of Chignik, Alaska · 29 km S of this epicentre
  5. 6.0 223 km SSW of Akhiok, Alaska · 39 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 55.4323, -155.6767. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.0 162 km ESE of Chignik, Alaska
  2. 3.0 154 km SW of Akhiok, Alaska
  3. 2.4 186 km SSW of Akhiok, Alaska
  4. 2.5 164 km ESE of Chignik, Alaska
  5. 2.7 223 km SSW of Akhiok, Alaska
  6. 2.2 167 km SW of Akhiok, Alaska
  7. 3.4 183 km SSW of Akhiok, Alaska
  8. 2.8 178 km SSW of Akhiok, Alaska
  9. 2.9 186 km SSW of Akhiok, Alaska
  10. 3.6 160 km SSW of Akhiok, Alaska
  11. 2.7 167 km SE of Chignik, Alaska
  12. 2.6 149 km SW of Akhiok, Alaska
  13. 3.8 184 km SSW of Akhiok, Alaska
  14. 2.4 south of Alaska
  15. 4.1 south of 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.