QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9mb

130 km WSW of Adak, Alaska

· 11 km deep · released about 11 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N
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 3.9 (mb)
Depth
11 km below the surface
Felt
no reports yet
Measured shaking
intensity II (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1146 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

How big was it?

This earthquake released about 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
  3. Magna, Utah 2020 M 5.7 500× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× 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 51.4519, -178.3970. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.1 138 km W of Adak, Alaska
  2. 2.6 129 km WSW of Adak, Alaska
  3. 2.8 133 km WSW of Adak, Alaska
  4. 3.9 129 km WSW of Adak, Alaska
  5. 4.1 130 km WSW of Adak, Alaska
  6. 2.5 126 km WSW of Adak, Alaska
  7. 2.3 145 km WSW of Adak, Alaska
  8. 3.1 127 km WSW of Adak, Alaska
  9. 2.1 126 km WSW of Adak, Alaska
  10. 2.0 128 km WSW of Adak, Alaska
  11. 2.8 128 km W of Adak, Alaska
  12. 2.9 136 km W of Adak, Alaska
  13. 2.4 123 km WSW of Adak, Alaska
  14. 3.2 129 km W of Adak, Alaska
  15. 3.2 Andreanof Islands, Aleutian Islands, 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 6.2 on 2017-05-08 — it released about 2,800 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.