QuakeIndex

Earthquake · reviewed by a seismologist

M 4.8ml

137 km ESE of Chignik, Alaska

· 45 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
45 km below the surface
Felt
1 report · strongest reported intensity II
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 278 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 55.8999, -156.3121. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.9 137 km ESE of Chignik, Alaska
  2. 2.4 111 km E of Chignik, Alaska
  3. 2.7 119 km E of Chignik, Alaska
  4. 2.6 114 km E of Chignik, Alaska
  5. 2.8 115 km E of Chignik, Alaska
  6. 3.4 111 km E of Chignik, Alaska
  7. 3.3 116 km E of Chignik, Alaska
  8. 4.1 114 km E of Chignik, Alaska
  9. 3.1 115 km E of Chignik, Alaska
  10. 2.3 116 km E of Chignik, Alaska
  11. 2.6 121 km E of Chignik, Alaska
  12. 2.4 113 km E of Chignik, Alaska
  13. 2.3 136 km E of Chignik, Alaska
  14. 3.6 115 km E of Chignik, Alaska
  15. 2.2 114 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.

For this area

The largest earthquake within 50 km in our catalogue was M 4.5 on 2021-07-29.

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

On USGS

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