QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1ml

24 km NNW of Old Harbor, Alaska

Yes. A magnitude 3.1 earthquake was recorded 24 km NNW of Old Harbor, Alaska, at 5:06 pm AKDT on 6 August 2023 (01:06 UTC), 43 km deep.

· 43 km deep · released about 1,300 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Kodiak Island Borough 44 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 3.1 (ml)
Depth
43 km below the surface
Felt
no reports yet
Nearest
Kodiak Island Borough, 44 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1123 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 1,300 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 250,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 11,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 7,900× the energy of this one
  4. This earthquake M 3.1 about 1,300 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.4× 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 4.9 on 2021-01-03 — about 500 times the energy of this one.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 24 km SSW of Larsen Bay, Alaska · 47 km W of this epicentre
  2. 6.2 19 km SW of Old Harbor, Alaska · 37 km SSW of this epicentre
  3. 6.0 15 km S of Larsen Bay, Alaska · 36 km W of this epicentre
  4. 5.9 25 km E of Old Harbor, Alaska · 43 km SE of this epicentre
  5. 5.7 24 km S of Larsen Bay, Alaska · 35 km WSW 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 57.4107, -153.4250. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Kodiak Island Borough, AK 44 km (27 mi) NW earthquakes near Kodiak Island Borough

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

Aftershocks so far

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

  1. 2.1 21 km S of Old Harbor, Alaska
  2. 1.5 20 km S of Larsen Bay, Alaska
  3. 3.1 31 km W of Old Harbor, Alaska
  4. 1.6 9 km S of Old Harbor, Alaska
  5. 1.5 36 km WSW of Womens Bay, Alaska
  6. 2.0 28 km SW of Womens Bay, Alaska
  7. 1.9 29 km SW of Old Harbor, Alaska
  8. 1.6 27 km ENE of Akhiok, Alaska
  9. 2.2 25 km E of Larsen Bay, Alaska
  10. 1.9 33 km SW of Port Lions, Alaska
  11. 2.3 15 km NE of Larsen Bay, Alaska
  12. 1.5 24 km NE of Larsen Bay, Alaska
  13. 1.8 20 km NNW of Old Harbor, Alaska
  14. 3.4 27 km ENE of Larsen Bay, Alaska
  15. 2.7 26 km NE of Akhiok, 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.