QuakeIndex

Earthquake · reviewed by a seismologist

M 5.4mww

166 km SSW of Adak, Alaska

Yes. A magnitude 5.4 earthquake was recorded 166 km SSW of Adak, Alaska at 21:24 UTC on 2019-09-09, 10 km deep. 1 person has reported feeling it to USGS.

· 10 km deep · released about 1.9 kilotons of TNT

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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 5.4 (mww)
Depth
10 km below the surface
Felt
1 report · strongest reported intensity III
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Nearest mapped fault
Alaska-Aleutian subduction zone, 1 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 326 days ago

This was a moderate earthquake. Shaking at this size can damage poorly built structures close to the epicentre.

At this magnitude and depth, people at rest would likely notice it out to about 246 km (153 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 1.9 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 6.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 89× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 4× the energy of this one
  3. Magna, Utah 2020 M 5.7 2.8× the energy of this one
  4. This earthquake M 5.4 about 1.9 kilotons of TNT
  5. Around the size people start to feel M 3.0 this one released 4,000× 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 4.3 on 2019-06-30.

Before 2016, the USGS record lists 18 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 184 km SSW of Adak, Alaska · 29 km WSW of this epicentre
  2. 6.4 146 km S of Adak, Alaska · 29 km NE of this epicentre
  3. 6.1 198 km S of Adak, Alaska · 40 km SSE of this epicentre
  4. 6.1 189 km S of Adak, Alaska · 27 km SSE of this epicentre
  5. 6.0 130 km SSW of Adak, Alaska · 50 km NNW 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 50.4146, -177.1730. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.6 171 km S of Adak, Alaska
  2. 2.2 188 km S of Adak, Alaska
  3. 2.0 196 km S of Adak, Alaska
  4. 1.7 189 km SSW of Adak, Alaska
  5. 2.7 212 km S of Adak, Alaska
  6. 3.4 167 km S of Adak, Alaska
  7. 2.2 156 km S of Adak, Alaska
  8. 3.7 164 km SSW of Adak, Alaska
  9. 2.2 Andreanof Islands, Aleutian Islands, Alaska
  10. 2.2 167 km S of Adak, Alaska
  11. 4.0 Andreanof Isl., Aleutian Islands, Alaska
  12. 2.7 213 km SSW of Adak, Alaska
  13. 2.3 147 km S of Adak, Alaska
  14. 3.1 178 km SSW of Adak, Alaska
  15. 2.3 178 km S 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.