QuakeIndex

Earthquake · reviewed by a seismologist

M 1.9ml

109 km E of Chignik, Alaska

Yes. A magnitude 1.9 earthquake was recorded 109 km E of Chignik, Alaska at 10:48 UTC on 2021-12-15, 65 km deep.

· 65 km deep · released about 21 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 1.9 (ml)
Depth
65 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1765 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause 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 21 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 710,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 500,000× the energy of this one
  3. Around the size people start to feel M 3.0 45× the energy of this one
  4. This earthquake M 1.9 about 21 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 32,000,000 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 · 21 km NE of this epicentre
  2. 6.4 77 km ESE of Chignik, Alaska · 48 km SW of this epicentre
  3. 6.4 104 km SSE of Ugashik, Alaska · 23 km NNW of this epicentre
  4. 6.3 112 km E of Chignik, Alaska · 29 km S of this epicentre
  5. 6.1 132 km E of Chignik, Alaska · 36 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 56.4476, -156.6502. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.3 124 km E of Chignik, Alaska
  2. 2.0 Alaska Peninsula
  3. 3.0 94 km ESE of Chignik, Alaska
  4. 1.8 112 km ENE of Chignik, Alaska
  5. 2.5 113 km SSE of Ugashik, Alaska
  6. 2.1 113 km SSE of Ugashik, Alaska
  7. 2.2 109 km E of Chignik, Alaska
  8. 2.3 118 km E of Chignik, Alaska
  9. 2.1 82 km SSE of Ugashik, Alaska
  10. 1.6 Alaska Peninsula
  11. 1.6 106 km SSE of Ugashik, Alaska
  12. 1.6 101 km SSE of Ugashik, Alaska
  13. 4.6 112 km SSE of Ugashik, Alaska
  14. 1.8 110 km E of Chignik, Alaska
  15. 2.2 123 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.