QuakeIndex

Earthquake · reviewed by a seismologist

M 5.2mb

165 km SE of Nikolski, Alaska

Yes. A magnitude 5.2 earthquake was recorded 165 km SE of Nikolski, Alaska at 01:01 UTC on 2021-12-05, 10 km deep. 5 people have reported feeling it to USGS.

· 10 km deep · released about 950 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 5.2 (mb)
Depth
10 km below the surface
Felt
5 reports · strongest reported intensity III
Measured shaking
intensity III (ShakeMap)
Nearest mapped fault
Alaska-Aleutian subduction zone, 10 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 1091 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 218 km (135 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 950 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.2 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 180× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 7.9× the energy of this one
  3. Magna, Utah 2020 M 5.7 5.6× the energy of this one
  4. This earthquake M 5.2 about 950 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 2,000× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.9 on 2017-12-10.

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

  1. 5.9 163 km SE of Nikolski, Alaska · 11 km NE of this epicentre
  2. 5.8 193 km SE of Nikolski, Alaska · 36 km S of this epicentre
  3. 5.4 202 km SE of Nikolski, Alaska · 43 km SSE of this epicentre
  4. 5.3 168 km SE of Nikolski, Alaska · 14 km NE of this epicentre
  5. 5.2 194 km SE of Nikolski, Alaska · 32 km ESE 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 51.9366, -167.0658. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.6 148 km SE of Nikolski, Alaska
  2. 2.3 149 km SE of Nikolski, Alaska
  3. 2.2 Fox Islands, Aleutian Islands, Alaska
  4. 2.8 149 km ESE of Nikolski, Alaska
  5. 2.3 125 km ESE of Nikolski, Alaska
  6. 2.2 171 km SE of Nikolski, Alaska
  7. 2.7 189 km SE of Nikolski, Alaska
  8. 2.9 184 km SE of Nikolski, Alaska
  9. 1.8 120 km SE of Nikolski, Alaska
  10. 1.9 148 km SE of Nikolski, Alaska
  11. 2.1 192 km SE of Nikolski, Alaska
  12. 2.4 162 km ESE of Nikolski, Alaska
  13. 2.7 143 km ESE of Nikolski, Alaska
  14. 2.8 south of the Aleutian Islands
  15. 2.1 168 km SE of Nikolski, 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.