QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

Kenai Peninsula, Alaska

Yes. A magnitude 1.8 earthquake was recorded in the Kenai Peninsula, Alaska, at 3:46 am AKST on 26 February 2023 (12:46 UTC), 18 km deep.

· 18 km deep · released about 15 lb 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 1.8 (ml)
Depth
18 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1351 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 4.7 on 2023-02-24 — about 22,000 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 5.7 78 km SSE of Port Graham, Alaska · 30 km S of this epicentre
  2. 5.7 30 km ESE of Port Graham, Alaska · 25 km NNW of this epicentre
  3. 5.4 22 km ESE of Port Graham, Alaska · 32 km NNW of this epicentre
  4. 5.3 16 km SE of Seldovia, Alaska · 40 km NNW of this epicentre
  5. 5.0 49 km SE of Port Graham, Alaska · 8 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 59.0235, -151.1804. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.2 76 km SSE of Halibut Cove, Alaska
  2. 4.9 8 km SE of Seldovia Village, Alaska
  3. 3.0 8 km SE of Seldovia Village, Alaska
  4. 2.1 56 km SE of Port Graham, Alaska
  5. 3.0 66 km SE of Port Graham, Alaska
  6. 1.8 17 km SE of Port Graham, Alaska
  7. 1.8 26 km SSE of Halibut Cove, Alaska
  8. 2.0 42 km SSE of Port Graham, Alaska
  9. 1.6 37 km SE of Seldovia Village, Alaska
  10. 2.1 52 km SE of Port Graham, Alaska
  11. 1.5 85 km SSE of Port Graham, Alaska
  12. 1.8 43 km SSE of Halibut Cove, Alaska
  13. 2.6 62 km SE of Port Graham, Alaska
  14. 2.9 8 km SSE of Seldovia, Alaska
  15. 2.1 20 km S of Halibut Cove, 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.