QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5ml

28 km N of Paxson, Alaska

· 5.1 km deep · released about 2.7 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 3.5 (ml)
Depth
5.1 km below the surface
Felt
1 report · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
Nearest
Southeast Fairbanks Census Area, 127 km ENE
Nearest mapped fault
Denali fault, under 1 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 1749 days ago

A magnitude 3.5 earthquake was recorded 28 km N of Paxson, Alaska at 06:18 UTC on 2021-10-11. 1 person has reported feeling it to USGS. This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

How big was it?

This earthquake released about 2.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 63,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2,800× the energy of this one
  3. Magna, Utah 2020 M 5.7 2,000× the energy of this one
  4. This earthquake M 3.5 about 2.7 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 5.6× 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.2 30 km SSW of Fort Greely, Alaska · 41 km NNW of this epicentre
  2. 5.7 31 km NNE of Paxson, Alaska · 7 km E of this epicentre
  3. 5.6 23 km NNW of Paxson, Alaska · 11 km WSW of this epicentre
  4. 5.6 23 km N of Paxson, Alaska · 10 km WSW of this epicentre
  5. 5.4 19 km NNE of Paxson, Alaska · 9 km S 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 63.3385, -145.5068. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Southeast Fairbanks Census Area, AK 127 km (79 mi) ENE earthquakes near Southeast Fairbanks Census Area

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

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

  1. 1.7 24 km NNE of Paxson, Alaska
  2. 1.6 20 km NE of Paxson, Alaska
  3. 2.3 35 km NE of Paxson, Alaska
  4. 2.1 26 km SW of Deltana, Alaska
  5. 1.6 27 km NNE of Paxson, Alaska
  6. 2.3 Central Alaska
  7. 1.5 Central Alaska
  8. 1.7 30 km NNE of Paxson, Alaska
  9. 1.9 29 km NNE of Paxson, Alaska
  10. 1.6 26 km NNE of Paxson, Alaska
  11. 1.6 27 km NNE of Paxson, Alaska
  12. 1.5 27 km NNE of Paxson, Alaska
  13. 2.4 29 km NNE of Paxson, Alaska
  14. 1.9 27 km NNE of Paxson, Alaska
  15. 1.7 32 km NE of Paxson, 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.