QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2ml

41 km SSW of Ugashik, Alaska

Yes. A magnitude 4.2 earthquake was recorded 41 km SSW of Ugashik, Alaska at 15:17 UTC on 2016-04-02, 12 km deep.

· 12 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 (ml)
Depth
12 km below the surface
Felt
no reports yet
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Nearest
Lake and Peninsula Borough, 129 km NE
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 since 2016 was M 6.2 on 2016-04-02 — about 1,000 times the energy of this one.

Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:

  1. 5.1 68 km S of Ugashik, Alaska · 40 km SE 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 57.1710, -157.6870. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Lake and Peninsula Borough, AK 129 km (80 mi) NE earthquakes near Lake and Peninsula Borough

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

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

  1. 2.1 58 km E of Port Heiden, Alaska
  2. 3.3 52 km SSW of Ugashik, Alaska
  3. 2.3 53 km SSW of Ugashik, Alaska
  4. 2.9 60 km S of Ugashik, Alaska
  5. 2.8 64 km E of Port Heiden, Alaska
  6. 3.6 49 km SSW of Ugashik, Alaska
  7. 2.4 60 km S of Ugashik, Alaska
  8. 2.6 41 km SSW of Ugashik, Alaska
  9. 3.2 48 km ENE of Port Heiden, Alaska
  10. 3.2 42 km SSW of Ugashik, Alaska
  11. 2.3 42 km NE of Port Heiden, Alaska
  12. 2.7 33 km E of Port Heiden, Alaska
  13. 2.5 48 km E of Port Heiden, Alaska
  14. 2.2 63 km E of Port Heiden, Alaska
  15. 2.4 63 km E of Port Heiden, 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.