QuakeIndex

Earthquake · reviewed by a seismologist

M 2.0ml

Earthquake near Tok, AK

USGS: 26 km SSW of Tanacross, Alaska

9:11 am AKDT, Apr 4, 2021 · · 16 km deep · released about 30 lb of TNT

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10 km30 km60 km120 km N Southeast Fairbanks Census Area 80 km
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
9:11 am AKDT on 4 April 2021 ()
Where
33 km (21 mi) SW of Tok, AK · earthquakes near Tok
Magnitude
M 2.0 (ml)
Depth
16 km below the surface
Felt
no reports yet
Nearest
Southeast Fairbanks Census Area, 80 km N
Nearest mapped fault
Cathedral Rapids faults (Northern Foothills fold and thrust belt), 16 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 1981 days ago

A magnitude 2.0 earthquake was recorded 33 km (21 mi) SW of Tok, AK, at 9:11 am AKDT on 4 April 2021 (17:11 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 30 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.0 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 500,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 350,000× the energy of this one
  3. Around the size people start to feel M 3.0 32× the energy of this one
  4. This earthquake M 2.0 about 30 lb of TNT

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 4.2 on 2020-10-26 — about 2,000 times the energy of this one.

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

  1. 5.9 44 km WNW of Mentasta Lake, Alaska · 50 km W of this epicentre
  2. 5.1 3 km ENE of Mentasta Lake, Alaska · 27 km SSW of this epicentre
  3. 5.1 17 km ESE of Mentasta Lake, Alaska · 33 km S of this epicentre
  4. 5.0 16 km WNW of Mentasta Lake, Alaska · 33 km SW 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 63.1578, -143.5135. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Southeast Fairbanks Census Area, AK 80 km (50 mi) N 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. 1.6 7 km NE of Slana, Alaska
  2. 3.0 13 km ENE of Slana, Alaska
  3. 2.3 13 km SE of Mentasta Lake, Alaska
  4. 3.1 13 km N of Mentasta Lake, Alaska
  5. 1.5 14 km SE of Mentasta Lake, Alaska
  6. 2.0 29 km SW of Tetlin, Alaska
  7. 1.7 13 km E of Slana, Alaska
  8. 2.1 29 km SW of Tetlin, Alaska
  9. 1.8 26 km E of Slana, Alaska
  10. 1.8 24 km SE of Mentasta Lake, Alaska
  11. 1.7 26 km SSW of Tanacross, Alaska
  12. 2.2 22 km SW of Tanacross, Alaska
  13. 1.6 25 km SSW of Tanacross, Alaska
  14. 2.2 24 km SW of Tanacross, Alaska
  15. 1.8 7 km SE of Mentasta Lake, 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.