QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7ml

Earthquake near Tok, AK

USGS: 29 km SW of Tanacross, Alaska

11:04 am AKDT, Aug 18, 2020 · · 5.2 km deep · released about 11 lb of TNT

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10 km30 km60 km120 km N Southeast Fairbanks Census Area 76 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
11:04 am AKDT on 18 August 2020 ()
Where
44 km (27 mi) WSW of Tok, AK · earthquakes near Tok
Magnitude
M 1.7 (ml)
Depth
5.2 km below the surface
Felt
no reports yet
Nearest
Southeast Fairbanks Census Area, 76 km NNE
Nearest mapped fault
Cathedral Rapids faults (Northern Foothills fold and thrust belt), 14 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 2219 days ago

A magnitude 1.7 earthquake was recorded 44 km (27 mi) WSW of Tok, AK, at 11:04 am AKDT on 18 August 2020 (19:04 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 11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,400,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
  3. Around the size people start to feel M 3.0 89× the energy of this one
  4. This earthquake M 1.7 about 11 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 4.0 on 2019-10-10 — about 2,800 times the energy of this one.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.9 44 km WNW of Mentasta Lake, Alaska · 35 km WSW of this epicentre
  2. 5.4 45 km WNW of Mentasta Lake, Alaska · 44 km WSW of this epicentre
  3. 5.2 41 km ENE of Paxson, Alaska · 49 km W of this epicentre
  4. 5.1 3 km ENE of Mentasta Lake, Alaska · 35 km S of this epicentre
  5. 5.1 44 km ENE of Paxson, Alaska · 46 km W 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 63.2383, -143.8376. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Southeast Fairbanks Census Area, AK 76 km (47 mi) NNE earthquakes near Southeast Fairbanks Census Area

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

Aftershocks so far

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

  1. 2.4 30 km WNW of Mentasta Lake, Alaska
  2. 2.2 37 km NW of Mentasta Lake, Alaska
  3. 2.4 37 km NW of Mentasta Lake, Alaska
  4. 2.5 36 km NW of Mentasta Lake, Alaska
  5. 1.7 39 km NW of Mentasta Lake, Alaska
  6. 1.6 5 km SSE of Mentasta Lake, Alaska
  7. 1.8 24 km NE of Mentasta Lake, Alaska
  8. 2.1 37 km NW of Mentasta Lake, Alaska
  9. 2.6 17 km ESE of Mentasta Lake, Alaska
  10. 1.5 9 km SE of Mentasta Lake, Alaska
  11. 1.7 36 km NW of Mentasta Lake, Alaska
  12. 1.8 35 km WSW of Tanacross, Alaska
  13. 1.9 16 km SE of Mentasta Lake, Alaska
  14. 3.0 43 km NW of Mentasta Lake, Alaska
  15. 1.6 Central 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.