QuakeIndex

Earthquake · automatic estimate, may change

M 1.8ml

Kodiak Island region, Alaska

Yes. A magnitude 1.8 earthquake was recorded in the Kodiak Island region, Alaska, at 7:38 am AKDT on 4 April 2021 (15:38 UTC), 76 km deep. The magnitude and location are an automatic first estimate and may change.

· 76 km deep · released about 15 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Kodiak Island Borough 74 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 1.8 (ml)
Depth
76 km below the surface
Felt
no reports yet
Nearest
Kodiak Island Borough, 74 km S
Status
Automatic — a machine’s first estimate, which may change

USGS · last changed by USGS · we first saw it 2049 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 15 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,000,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 710,000× the energy of this one
  3. Around the size people start to feel M 3.0 63× the energy of this one
  4. This earthquake M 1.8 about 15 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

The largest earthquake within 50 km since 2016 was M 5.6 on 2017-08-31 — about 500,000 times the energy of this one.

Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.2 37 km NNW of Aleneva, Alaska · 36 km E of this epicentre
  2. 5.7 76 km WNW of Aleneva, Alaska · 14 km W of this epicentre
  3. 5.7 40 km WNW of Aleneva, Alaska · 24 km SE of this epicentre
  4. 5.5 91 km WNW of Aleneva, Alaska · 28 km WNW of this epicentre
  5. 5.4 81 km WNW of Aleneva, Alaska · 18 km WNW 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 58.3671, -153.8321. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Kodiak Island Borough, AK 74 km (46 mi) S earthquakes near Kodiak Island Borough

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

Aftershocks so far

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

  1. 1.5 80 km NNW of Aleneva, Alaska
  2. 1.6 84 km NW of Aleneva, Alaska
  3. 1.5 99 km WNW of Aleneva, Alaska
  4. 1.6 92 km NNW of Aleneva, Alaska
  5. 1.9 87 km NW of Aleneva, Alaska
  6. 1.6 88 km NNW of Aleneva, Alaska
  7. 1.5 88 km NNW of Aleneva, Alaska
  8. 3.2 52 km WNW of Aleneva, Alaska
  9. 1.6 Alaska Peninsula
  10. 4.4 73 km NNE of Karluk, Alaska
  11. 1.6 84 km NNW of Aleneva, Alaska
  12. 1.7 90 km NNW of Aleneva, Alaska
  13. 1.6 86 km NNW of Aleneva, Alaska
  14. 1.7 82 km NNW of Aleneva, Alaska
  15. 1.6 91 km NNW of Aleneva, 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.