QuakeIndex

Earthquake · reviewed by a seismologist

M 4.8mb

103 km NNE of Adak, Alaska

Yes. A magnitude 4.8 earthquake was recorded 103 km NNE of Adak, Alaska at 04:13 UTC on 2020-04-27, 224 km deep.

· 224 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 (mb)
Depth
224 km below the surface
Felt
no reports yet
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 2316 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth it was probably too small to be felt, even directly above it. 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 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.

For this area

The largest earthquake within 50 km (31 mi) since our catalogue begins in 2016. The previous largest was M 4.7 on 2017-01-13.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

  1. 5.4 94 km NNE of Adak, Alaska · 10 km SSW of this epicentre
  2. 5.3 56 km NNE of Adak, Alaska · 47 km SSW of this epicentre
  3. 5.1 82 km NNE of Adak, Alaska · 25 km S 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 52.7406, -176.0667. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.0 66 km N of Adak, Alaska
  2. 2.8 72 km NNE of Adak, Alaska
  3. 3.4 86 km NE of Adak, Alaska
  4. 3.2 Andreanof Islands, Aleutian Islands, Alaska
  5. 2.7 59 km NNE of Adak, Alaska
  6. 4.1 77 km NNE of Adak, Alaska
  7. 3.0 67 km NE of Adak, Alaska
  8. 2.3 83 km NE of Adak, Alaska
  9. 2.5 92 km NNE of Adak, Alaska
  10. 4.0 81 km NE of Adak, Alaska
  11. 2.0 69 km NE of Adak, Alaska
  12. 4.1 86 km NNE of Adak, Alaska
  13. 1.8 86 km NE of Adak, Alaska
  14. 2.8 73 km NE of Adak, Alaska
  15. 2.3 68 km NE of Adak, 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.