QuakeIndex

Earthquake · reviewed by a seismologist

M 3.3ml

117 km SSE of Ugashik, Alaska

Yes. A magnitude 3.3 earthquake was recorded 117 km SSE of Ugashik, Alaska at 10:14 UTC on 2024-03-31, 55 km deep. 1 person has reported feeling it to USGS.

· 55 km deep · released about 1.3 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 3.3 (ml)
Depth
55 km below the surface
Felt
1 report · strongest reported intensity III
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 895 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. 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 1.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 130,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 5,600× the energy of this one
  3. Magna, Utah 2020 M 5.7 4,000× the energy of this one
  4. This earthquake M 3.3 about 1.3 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 2.8× 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 6.9 on 2021-10-11 — about 250,000 times the energy of this one.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.8 117 km SSE of Ugashik, Alaska · 3 km SW of this epicentre
  2. 6.4 104 km SSE of Ugashik, Alaska · 21 km WNW of this epicentre
  3. 6.3 112 km E of Chignik, Alaska · 49 km SSW of this epicentre
  4. 6.1 132 km E of Chignik, Alaska · 46 km S of this epicentre
  5. 5.4 115 km SSE of Ugashik, Alaska · 4 km NNE 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 56.6084, -156.3936. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.9 90 km SSE of Ugashik, Alaska
  2. 2.1 126 km WSW of Akhiok, Alaska
  3. 1.8 119 km SSE of Ugashik, Alaska
  4. 2.2 104 km W of Akhiok, Alaska
  5. 1.5 110 km W of Akhiok, Alaska
  6. 1.7 105 km SSE of Ugashik, Alaska
  7. 2.6 128 km E of Chignik, Alaska
  8. 2.2 130 km WSW of Akhiok, Alaska
  9. 1.6 105 km W of Akhiok, Alaska
  10. 1.7 119 km E of Chignik, Alaska
  11. 2.1 74 km SSE of Ugashik, Alaska
  12. 1.9 93 km SSE of Ugashik, Alaska
  13. 1.5 89 km SE of Ugashik, Alaska
  14. 1.5 89 km SE of Ugashik, Alaska
  15. 1.5 106 km SE of Ugashik, 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.