QuakeIndex

Earthquake · reviewed by a seismologist

M 3.3ml

84 km SSE of False Pass, Alaska

Yes. A magnitude 3.3 earthquake was recorded 84 km SSE of False Pass, Alaska, at 11:43 am AKDT on 9 May 2021 (19:43 UTC), 13 km deep.

· 13 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
13 km below the surface
Felt
no reports yet
Nearest
Aleutians East Borough, 130 km NNE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1939 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, people at rest would likely notice it out to about 50 km (31 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 1.3 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 5.0 on 2020-08-20 — about 350 times the energy of this one.

Before 2016, the USGS record lists 24 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 47 km SE of False Pass, Alaska · 43 km N of this epicentre
  2. 6.5 88 km SE of False Pass, Alaska · 14 km ENE of this epicentre
  3. 5.8 112 km SE of False Pass, Alaska · 32 km ESE of this epicentre
  4. 5.8 60 km SSW of King Cove, Alaska · 43 km NNE of this epicentre
  5. 5.7 88 km SE of False Pass, Alaska · 15 km ENE 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 54.1797, -162.8145. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Aleutians East Borough, AK 130 km (81 mi) NNE earthquakes near Aleutians East Borough

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

Aftershocks so far

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

  1. 3.7 90 km SE of False Pass, Alaska
  2. 2.8 99 km SSE of False Pass, Alaska
  3. 3.6 102 km SSE of False Pass, Alaska
  4. 3.3 89 km SE of False Pass, Alaska
  5. 2.5 102 km S of King Cove, Alaska
  6. 3.1 79 km SSE of False Pass, Alaska
  7. 2.3 64 km S of False Pass, Alaska
  8. 4.0 111 km SE of False Pass, Alaska
  9. 3.0 100 km SE of False Pass, Alaska
  10. 2.9 114 km SSE of False Pass, Alaska
  11. 1.9 79 km SE of False Pass, Alaska
  12. 2.2 79 km S of King Cove, Alaska
  13. 2.3 93 km S of False Pass, Alaska
  14. 2.1 90 km SE of False Pass, Alaska
  15. 2.0 90 km S of King Cove, 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.