QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2mb

Andreanof Islands, Aleutian Islands, Alaska

Yes. A magnitude 4.2 earthquake was recorded in the Andreanof Islands, Aleutian Islands, Alaska at 15:51 UTC on 2016-07-24, 10 km deep.

· 10 km deep · released about 30 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 4.2 (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 1200 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, people at rest would likely notice it out to about 112 km (70 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 30 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 5,600× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 250× the energy of this one
  3. Magna, Utah 2020 M 5.7 180× the energy of this one
  4. This earthquake M 4.2 about 30 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 63× 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. No other earthquake of M4 or more has been recorded this close in that time.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 6.5 184 km SSW of Adak, Alaska · 32 km NE of this epicentre
  2. 6.0 194 km SSW of Adak, Alaska · 30 km ENE of this epicentre
  3. 5.8 192 km SSW of Adak, Alaska · 25 km NE of this epicentre
  4. 5.5 168 km SSW of Adak, Alaska · 48 km NE of this epicentre
  5. 5.1 190 km SSW of Adak, Alaska · 27 km NE 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 50.0965, -177.8373. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.4 179 km SSW of Adak, Alaska
  2. 3.0 214 km SSW of Adak, Alaska
  3. 3.0 217 km SSW of Adak, Alaska
  4. 2.4 227 km SSW of Adak, Alaska
  5. 3.1 178 km SSW of Adak, Alaska
  6. 3.3 188 km SSW of Adak, Alaska
  7. 2.3 238 km SSW of Adak, Alaska
  8. 2.6 217 km SSW of Adak, Alaska
  9. 3.5 237 km SSW of Adak, Alaska
  10. 2.3 179 km SSW of Adak, Alaska
  11. 3.9 177 km SSW of Adak, Alaska
  12. 3.4 204 km SSW of Adak, Alaska
  13. 2.1 186 km SSW of Adak, Alaska
  14. 2.1 226 km SSW of Adak, Alaska
  15. 1.9 211 km SSW 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.