QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9mb

96 km SSW of Sand Point, Alaska

Yes. A magnitude 3.9 earthquake was recorded 96 km SSW of Sand Point, Alaska, at 2:49 am AKST on 4 January 2021 (11:49 UTC), 38 km deep.

· 38 km deep · released about 11 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Aleutians East Borough 113 km
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 3.9 (mb)
Depth
38 km below the surface
Felt
no reports yet
Nearest
Aleutians East Borough, 113 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2071 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 81 km (50 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 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
  3. Magna, Utah 2020 M 5.7 500× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× 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 6.1 on 2020-07-28 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 30 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 90 km SE of King Cove, Alaska · 25 km WNW of this epicentre
  2. 6.8 73 km SW of Sand Point, Alaska · 46 km NW of this epicentre
  3. 6.6 72 km SE of King Cove, Alaska · 49 km WNW of this epicentre
  4. 6.4 101 km SSW of Sand Point, Alaska · 17 km W of this epicentre
  5. 6.4 109 km SSE of King Cove, Alaska · 49 km SW 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 54.4923, -160.8121. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Aleutians East Borough, AK 113 km (70 mi) NW earthquakes near Aleutians East Borough

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

Aftershocks so far

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

  1. 2.0 88 km SSW of Sand Point, Alaska
  2. 3.1 111 km S of Sand Point, Alaska
  3. 1.8 73 km SE of King Cove, Alaska
  4. 1.8 76 km SE of King Cove, Alaska
  5. 1.8 75 km SE of King Cove, Alaska
  6. 2.1 104 km SE of King Cove, Alaska
  7. 1.9 77 km SE of King Cove, Alaska
  8. 1.9 89 km SE of King Cove, Alaska
  9. 2.0 70 km S of Sand Point, Alaska
  10. 2.1 84 km SE of King Cove, Alaska
  11. 2.0 Alaska Peninsula
  12. 2.6 85 km SE of King Cove, Alaska
  13. 4.8 75 km ESE of King Cove, Alaska
  14. 1.6 64 km SSW of Sand Point, Alaska
  15. 1.7 84 km SSW of Sand Point, 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.