QuakeIndex

Earthquake · reviewed by a seismologist

M 5.4mww

119 km E of Chignik, Alaska

Yes. A magnitude 5.4 earthquake was recorded 119 km E of Chignik, Alaska at 03:33 UTC on 2022-04-28, 52 km deep. 8 people have reported feeling it to USGS.

· 52 km deep · released about 1.9 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 5.4 (mww)
Depth
52 km below the surface
Felt
8 reports · strongest reported intensity III
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1592 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 241 km (150 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 1.9 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 89× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 4× the energy of this one
  3. Magna, Utah 2020 M 5.7 2.8× the energy of this one
  4. This earthquake M 5.4 about 1.9 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 4,000× 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 since 2016 was M 6.9 on 2021-10-11 — about 180 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 · 29 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 · 37 km NNW of this epicentre
  4. 6.3 112 km E of Chignik, Alaska · 19 km SSW of this epicentre
  5. 6.1 132 km E of Chignik, Alaska · 20 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 56.3385, -156.4799. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.4 116 km E of Chignik, Alaska
  2. 1.8 112 km SSE of Ugashik, Alaska
  3. 2.5 108 km E of Chignik, Alaska
  4. 2.2 119 km E of Chignik, Alaska
  5. 2.3 113 km E of Chignik, Alaska
  6. 2.0 128 km WSW of Akhiok, Alaska
  7. 1.7 115 km E of Chignik, Alaska
  8. 2.6 116 km E of Chignik, Alaska
  9. 2.0 124 km E of Chignik, Alaska
  10. 2.2 111 km E of Chignik, Alaska
  11. 1.6 111 km SSE of Ugashik, Alaska
  12. 1.8 109 km SSE of Ugashik, Alaska
  13. 1.7 115 km E of Chignik, Alaska
  14. 2.2 121 km E of Chignik, Alaska
  15. 2.2 118 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.