QuakeIndex

Earthquake · reviewed by a seismologist

M 6.4mww

78 km NNW of Adak, Alaska

Yes. A magnitude 6.4 earthquake was recorded 78 km NNW of Adak, Alaska at 11:35 UTC on 2023-10-16, 174 km deep. 12 people have reported feeling it to USGS.

· 174 km deep · released about 60 kilotons 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 6.4 (mww)
Depth
174 km below the surface
Felt
12 reports · strongest reported intensity V
Measured shaking
intensity V (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 409 days ago

This was a strong earthquake. Damage is likely near the epicentre and it is felt over a wide area.

At this magnitude and depth, people at rest would likely notice it out to about 393 km (244 mi) from the epicentre. 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 60 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 7.4 would have released about 32 times as much.

  1. Ridgecrest, California 2019 M 7.1 11× the energy of this one
  2. Loma Prieta, California 1989 M 6.9 5.6× the energy of this one
  3. Northridge, California 1994 M 6.7 2.8× the energy of this one
  4. This earthquake M 6.4 about 60 kilotons of TNT
  5. Mineral, Virginia 2011 M 5.8 this one released 7.9× more
  6. Magna, Utah 2020 M 5.7 this one released 11× 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 2016-10-22.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.0 108 km NNW of Adak, Alaska · 30 km N of this epicentre
  2. 5.5 105 km NNW of Adak, Alaska · 36 km WNW of this epicentre
  3. 5.3 56 km NNE of Adak, Alaska · 47 km ESE of this epicentre
  4. 5.2 85 km NNW of Adak, Alaska · 16 km W of this epicentre
  5. 5.1 46 km NW of Adak, Alaska · 43 km SSW 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 52.5592, -176.9240. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.4 30 km N of Adak, Alaska
  2. 3.1 48 km N of Adak, Alaska
  3. 3.6 34 km NNW of Adak, Alaska
  4. 3.7 43 km N of Adak, Alaska
  5. 3.3 40 km NNW of Adak, Alaska
  6. 2.2 87 km N of Adak, Alaska
  7. 2.5 51 km NNE of Adak, Alaska
  8. 2.9 46 km N of Adak, Alaska
  9. 2.4 44 km NNW of Adak, Alaska
  10. 2.0 69 km NW of Adak, Alaska
  11. 2.9 47 km N of Adak, Alaska
  12. 2.4 39 km NNE of Adak, Alaska
  13. 4.0 45 km NNE of Adak, Alaska
  14. 3.1 32 km N of Adak, Alaska
  15. 2.9 50 km NNE 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.