QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9mb

155 km WSW of Adak, Alaska

· 10 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
10 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2489 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 51.2664, -178.6557. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.6 154 km WSW of Adak, Alaska
  2. 2.7 131 km WSW of Adak, Alaska
  3. 1.9 176 km WSW of Adak, Alaska
  4. 1.7 184 km WSW of Adak, Alaska
  5. 1.5 150 km WSW of Adak, Alaska
  6. 2.0 150 km WSW of Adak, Alaska
  7. 2.7 127 km WSW of Adak, Alaska
  8. 1.7 142 km WSW of Adak, Alaska
  9. 2.7 123 km WSW of Adak, Alaska
  10. 1.6 118 km WSW of Adak, Alaska
  11. 1.9 141 km WSW of Adak, Alaska
  12. 1.8 144 km WSW of Adak, Alaska
  13. 3.2 149 km WSW of Adak, Alaska
  14. 2.1 142 km WSW of Adak, Alaska
  15. 2.2 124 km WSW 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.

For this area

The largest earthquake within 50 km in our catalogue was M 6.0 on 2019-05-23 — it released about 1,400 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.