QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5ml

117 km E of Chignik, Alaska

Yes. A magnitude 2.5 earthquake was recorded 117 km E of Chignik, Alaska at 23:22 UTC on 2021-11-30, 72 km deep.

· 72 km deep · released about 170 lb 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 2.5 (ml)
Depth
72 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1741 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. 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 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
  3. Around the size people start to feel M 3.0 5.6× the energy of this one
  4. This earthquake M 2.5 about 170 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 6.9 on 2021-10-11 — about 4,000,000 times the energy of this one.

Before 2016, the USGS record lists 16 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.8 117 km SSE of Ugashik, Alaska · 26 km N of this epicentre
  2. 6.4 77 km ESE of Chignik, Alaska · 50 km WSW of this epicentre
  3. 6.4 104 km SSE of Ugashik, Alaska · 35 km NNW of this epicentre
  4. 6.3 112 km E of Chignik, Alaska · 21 km SSW of this epicentre
  5. 6.1 132 km E of Chignik, Alaska · 23 km SE 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 56.3623, -156.5014. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.3 118 km E of Chignik, Alaska
  2. 1.6 Alaska Peninsula
  3. 1.6 106 km SSE of Ugashik, Alaska
  4. 1.6 101 km SSE of Ugashik, Alaska
  5. 4.6 112 km SSE of Ugashik, Alaska
  6. 1.8 110 km E of Chignik, Alaska
  7. 2.2 123 km E of Chignik, Alaska
  8. 2.8 118 km E of Chignik, Alaska
  9. 2.2 100 km E of Chignik, Alaska
  10. 2.3 Alaska Peninsula
  11. 2.2 95 km ENE of Chignik, Alaska
  12. 2.0 124 km ESE of Chignik, Alaska
  13. 2.1 114 km E of Chignik, Alaska
  14. 2.4 106 km E of Chignik, Alaska
  15. 3.2 113 km E of Chignik, 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.