QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1ml

26 km S of Old Harbor, Alaska

Yes. A magnitude 2.1 earthquake was recorded 26 km S of Old Harbor, Alaska, at 8:01 am AKST on 23 February 2021 (17:01 UTC), 25 km deep.

· 25 km deep · released about 43 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Kodiak Island Borough 88 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 2.1 (ml)
Depth
25 km below the surface
Felt
no reports yet
Nearest
Kodiak Island Borough, 88 km NNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2073 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause 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 43 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 350,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 250,000× the energy of this one
  3. Around the size people start to feel M 3.0 22× the energy of this one
  4. This earthquake M 2.1 about 43 lb of TNT

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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 16 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 47 km S of Old Harbor, Alaska · 23 km SSE of this epicentre
  2. 6.2 19 km SW of Old Harbor, Alaska · 16 km NW of this epicentre
  3. 6.1 36 km ESE of Akhiok, Alaska · 21 km SW of this epicentre
  4. 5.9 25 km E of Old Harbor, Alaska · 36 km NE of this epicentre
  5. 5.9 56 km SE of Old Harbor, Alaska · 43 km ESE 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 56.9713, -153.3763. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Kodiak Island Borough, AK 88 km (55 mi) NNW 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. 3.1 27 km ESE of Akhiok, Alaska
  2. 2.0 35 km SE of Old Harbor, Alaska
  3. 1.9 25 km ENE of Akhiok, Alaska
  4. 1.9 29 km WSW of Old Harbor, Alaska
  5. 2.6 59 km SE of Akhiok, Alaska
  6. 2.2 25 km SE of Larsen Bay, Alaska
  7. 2.7 25 km W of Old Harbor, Alaska
  8. 1.5 23 km WNW of Old Harbor, Alaska
  9. 1.7 19 km ENE of Akhiok, Alaska
  10. 1.9 30 km SSE of Old Harbor, Alaska
  11. 2.1 26 km NNW of Old Harbor, Alaska
  12. 2.0 29 km SSE of Larsen Bay, Alaska
  13. 1.6 24 km WNW of Old Harbor, Alaska
  14. 1.5 26 km WNW of Old Harbor, Alaska
  15. 1.5 25 km ENE 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.