QuakeIndex

Earthquake · reviewed by a seismologist

M 4.8ml

113 km SSE of Chignik, Alaska

· 7.4 km deep · released about 240 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 4.8 (ml)
Depth
7.4 km below the surface
Felt
1 report · strongest reported intensity III
Measured shaking
intensity II (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1676 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 240 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 710× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 32× the energy of this one
  3. Magna, Utah 2020 M 5.7 22× the energy of this one
  4. This earthquake M 4.8 about 240 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 500× 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.

Where

Epicentre 55.4154, -157.4819. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.9 130 km SE of Perryville, Alaska
  2. 2.4 138 km SSE of Chignik, Alaska
  3. 4.4 119 km SE of Chignik, Alaska
  4. 3.0 111 km SE of Perryville, Alaska
  5. 1.9 109 km SE of Chignik, Alaska
  6. 3.2 114 km SE of Chignik, Alaska
  7. 3.0 123 km SE of Chignik, Alaska
  8. 3.5 125 km SE of Chignik, Alaska
  9. 4.3 Alaska Peninsula
  10. 2.2 126 km SE of Chignik, Alaska
  11. 3.9 126 km SE of Chignik, Alaska
  12. 2.2 112 km SE of Chignik, Alaska
  13. 3.3 124 km SE of Chignik, Alaska
  14. 4.3 112 km SE of Chignik, Alaska
  15. 1.6 90 km SE 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.

For this area

The largest earthquake within 50 km in our catalogue was M 8.2 on 2021-07-29 — it released about 130,000 times the energy of this one.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.