QuakeIndex

Earthquake · reviewed by a seismologist

M 5.5mww

45 km ESE of Nikolski, Alaska

Yes. A magnitude 5.5 earthquake was recorded 45 km ESE of Nikolski, Alaska at 04:59 UTC on 2020-11-30, 34 km deep. 5 people have reported feeling it to USGS.

· 34 km deep · released about 2.7 kilotons 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 5.5 (mww)
Depth
34 km below the surface
Felt
5 reports · strongest reported intensity III
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 327 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 259 km (161 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 2.7 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 63× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2.8× the energy of this one
  3. Magna, Utah 2020 M 5.7 2× the energy of this one
  4. This earthquake M 5.5 about 2.7 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 5,600× 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 2020-10-08 — about 2 times the energy of this one.

Before 2016, the USGS record lists 77 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 80 km E of Nikolski, Alaska · 47 km ENE of this epicentre
  2. 6.7 75 km SSE of Nikolski, Alaska · 48 km S of this epicentre
  3. 6.7 72 km ESE of Nikolski, Alaska · 26 km ESE of this epicentre
  4. 6.6 61 km SE of Nikolski, Alaska · 18 km SSE of this epicentre
  5. 6.5 45 km SSE of Nikolski, Alaska · 28 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 52.7448, -168.2605. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.1 51 km ESE of Nikolski, Alaska
  2. 2.9 50 km SE of Nikolski, Alaska
  3. 3.9 49 km ESE of Nikolski, Alaska
  4. 4.4 40 km ESE of Nikolski, Alaska
  5. 2.0 53 km ESE of Nikolski, Alaska
  6. 2.5 56 km ESE of Nikolski, Alaska
  7. 2.2 52 km ESE of Nikolski, Alaska
  8. 2.0 53 km ESE of Nikolski, Alaska
  9. 2.1 59 km ESE of Nikolski, Alaska
  10. 1.9 49 km ESE of Nikolski, Alaska
  11. 2.0 70 km ESE of Nikolski, Alaska
  12. 4.5 41 km ESE of Nikolski, Alaska
  13. 2.0 58 km ESE of Nikolski, Alaska
  14. 2.0 58 km ESE of Nikolski, Alaska
  15. 3.0 53 km ESE 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.