QuakeIndex

Earthquake · reviewed by a seismologist

M 4.8ml

135 km SE of Perryville, Alaska

· 26 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
26 km below the surface
Felt
7 reports · strongest reported intensity VIII
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1742 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon. 7 people have 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 55.0371, -157.6473. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.0 Alaska Peninsula
  2. 2.6 94 km SE of Perryville, Alaska
  3. 2.8 149 km SE of Perryville, Alaska
  4. 2.4 141 km SSE of Chignik, Alaska
  5. 3.2 123 km SE of Chignik, Alaska
  6. 2.5 101 km SE of Perryville, Alaska
  7. 2.6 133 km SE of Perryville, Alaska
  8. 2.4 158 km SE of Perryville, Alaska
  9. 2.6 152 km SSE of Chignik, Alaska
  10. 2.9 Alaska Peninsula
  11. 4.1 149 km SE of Perryville, Alaska
  12. 2.4 140 km SE of Perryville, Alaska
  13. 2.7 127 km SSE of Chignik, Alaska
  14. 2.6 140 km SSE of Chignik, Alaska
  15. 2.4 136 km SE of Perryville, 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.