QuakeIndex

Earthquake · reviewed by a seismologist

M 5.1mww

Unimak Island region, Alaska

Yes. A magnitude 5.1 earthquake was recorded in the Unimak Island region, Alaska at 07:19 UTC on 2021-01-11, 35 km deep.

· 35 km deep · released about 670 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 5.1 (mww)
Depth
35 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 326 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 203 km (126 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 670 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 250× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 11× the energy of this one
  3. Magna, Utah 2020 M 5.7 7.9× the energy of this one
  4. This earthquake M 5.1 about 670 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 1,400× 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 5.7 on 2020-08-13 — about 7.9 times the energy of this one.

Before 2016, the USGS record lists 69 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.6 146 km ESE of Akutan, Alaska · 19 km SE of this epicentre
  2. 6.6 92 km SE of Akutan, Alaska · 46 km W of this epicentre
  3. 6.5 81 km ESE of Akutan, Alaska · 49 km WNW of this epicentre
  4. 6.4 85 km ESE of Akutan, Alaska · 47 km W of this epicentre
  5. 6.2 Unimak Island region, Alaska · 12 km N 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 53.6763, -163.9531. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.0 105 km ESE of Akutan, Alaska
  2. 2.0 114 km ESE of Akutan, Alaska
  3. 2.7 165 km ESE of Akutan, Alaska
  4. 2.1 106 km ESE of Akutan, Alaska
  5. 1.8 99 km ESE of Akutan, Alaska
  6. 1.7 100 km ESE of Akutan, Alaska
  7. 2.6 160 km S of False Pass, Alaska
  8. 2.8 118 km ESE of Akutan, Alaska
  9. 3.5 100 km ESE of Akutan, Alaska
  10. 3.0 152 km S of False Pass, Alaska
  11. 3.9 149 km S of False Pass, Alaska
  12. 3.2 108 km ESE of Akutan, Alaska
  13. 1.5 103 km ESE of Akutan, Alaska
  14. 2.0 96 km SSW of False Pass, Alaska
  15. 1.8 116 km ESE of Akutan, 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.