QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9ml

73 km ESE of Sand Point, Alaska

Yes. A magnitude 3.9 earthquake was recorded 73 km ESE of Sand Point, Alaska, at 12:48 pm AKDT on 16 October 2024 (20:48 UTC), 12 km deep. 2 people have reported feeling it to USGS.

· 12 km deep · released about 11 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 3.9 (ml)
Depth
12 km below the surface
Felt
2 reports · strongest reported intensity II
Measured shaking
intensity IV (ShakeMap)
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 687 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 89 km (55 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 2020-07-22 — about 2,000 times the energy of this one.

Before 2016, the USGS record lists 18 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.4 54 km SE of Sand Point, Alaska · 33 km WSW of this epicentre
  2. 6.6 72 km SE of Sand Point, Alaska · 24 km SSW of this epicentre
  3. 6.6 104 km SSE of Perryville, Alaska · 50 km ESE of this epicentre
  4. 6.6 85 km SE of Sand Point, Alaska · 41 km SSW of this epicentre
  5. 6.5 94 km ESE of Sand Point, Alaska · 25 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 55.1148, -159.4059. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.9 62 km ESE of Sand Point, Alaska
  2. 2.1 73 km ESE of Sand Point, Alaska
  3. 1.7 46 km S of Perryville, Alaska
  4. 2.9 67 km SSE of Perryville, Alaska
  5. 2.0 62 km S of Ivanof Bay, Alaska
  6. 2.1 71 km E of Sand Point, Alaska
  7. 2.2 50 km ESE of Sand Point, Alaska
  8. 2.2 50 km E of Sand Point, Alaska
  9. 2.2 49 km S of Ivanof Bay, Alaska
  10. 2.3 58 km S of Ivanof Bay, Alaska
  11. 2.6 47 km SSW of Ivanof Bay, Alaska
  12. 2.2 55 km E of Sand Point, Alaska
  13. 2.3 57 km ESE of Sand Point, Alaska
  14. 2.1 60 km ESE of Sand Point, Alaska
  15. 2.3 72 km SSE 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.