QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9mb

106 km E of Chignik, Alaska

Yes. A magnitude 3.9 earthquake was recorded 106 km E of Chignik, Alaska at 14:17 UTC on 2022-05-01, 3.8 km deep. 1 person has reported feeling it to USGS.

· 3.8 km deep · released about 11 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 3.9 (mb)
Depth
3.8 km below the surface
Felt
1 report · strongest reported intensity III
Measured shaking
intensity III (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1587 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, people at rest would likely notice it out to about 89 km (55 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 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
  3. Magna, Utah 2020 M 5.7 500× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× 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 6.9 on 2021-10-11 — about 32,000 times the energy of this one.

Before 2016, the USGS record lists 14 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.0 113 km ESE of Chignik, Alaska · 39 km S of this epicentre
  2. 6.9 143 km ESE of Chignik, Alaska · 50 km SSE of this epicentre
  3. 6.8 117 km SSE of Ugashik, Alaska · 48 km NNE of this epicentre
  4. 6.4 77 km ESE of Chignik, Alaska · 31 km W of this epicentre
  5. 6.3 112 km E of Chignik, Alaska · 6 km E 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 56.1845, -156.6966. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 4.4 114 km E of Chignik, Alaska
  2. 1.9 111 km E of Chignik, Alaska
  3. 2.6 115 km E of Chignik, Alaska
  4. 1.9 95 km E of Chignik, Alaska
  5. 2.1 114 km E of Chignik, Alaska
  6. 1.7 82 km E of Chignik, Alaska
  7. 1.7 118 km SSE of Ugashik, Alaska
  8. 2.0 81 km E of Chignik, Alaska
  9. 2.4 110 km ENE of Chignik, Alaska
  10. 2.1 91 km ESE of Chignik, Alaska
  11. 2.4 111 km E of Chignik, Alaska
  12. 2.0 115 km E of Chignik, Alaska
  13. 2.5 115 km E of Chignik, Alaska
  14. 2.4 116 km E of Chignik, Alaska
  15. 1.8 112 km SSE of Ugashik, 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.