QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2mb

Gulf of Alaska

Yes. A magnitude 4.2 earthquake was recorded in the Gulf of Alaska at 13:29 UTC on 2016-02-15, 10 km deep.

· 10 km deep · released about 30 tons 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 4.2 (mb)
Depth
10 km below the surface
Felt
no reports yet
Nearest mapped fault
Gulf of Alaska shear zone, 21 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 1201 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 7 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.8 Gulf of Alaska · 21 km SE of this epicentre
  2. 5.8 296 km SW of Yakutat, Alaska · 49 km NNE of this epicentre
  3. 5.2 Gulf of Alaska · 9 km SSW of this epicentre
  4. 5.1 Gulf of Alaska · 42 km SSE of this epicentre
  5. 5.1 Gulf of Alaska · 23 km ESE 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 57.1036, -143.2535. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.4 Gulf of Alaska
  2. 2.7 Gulf of Alaska
  3. 3.1 Gulf of Alaska
  4. 2.7 Gulf of Alaska
  5. 2.7 Gulf of Alaska
  6. 2.6 Gulf of Alaska
  7. 3.0 Gulf of Alaska
  8. 2.2 Gulf of Alaska
  9. 2.5 Gulf of Alaska
  10. 2.8 Gulf of Alaska
  11. 3.4 Gulf of Alaska
  12. 2.4 Gulf of Alaska
  13. 2.8 Gulf of Alaska
  14. 2.1 Gulf of Alaska
  15. 2.2 299 km SW of Yakutat, 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.