QuakeIndex

Earthquake · reviewed by a seismologist

M 2.3ml

124 km S of Unalaska, Alaska

Yes. A magnitude 2.3 earthquake was recorded 124 km S of Unalaska, Alaska, at 9:59 am AKDT on 24 March 2021 (17:59 UTC), 5.0 km deep.

· 5.0 km deep · released about 85 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 2.3 (ml)
Depth
5.0 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2034 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 19 km (12 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 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
  3. Around the size people start to feel M 3.0 11× the energy of this one
  4. This earthquake M 2.3 about 85 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 5.4 on 2016-07-26 — about 45,000 times the energy of this one.

Before 2016, the USGS record lists 52 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 127 km E of Nikolski, Alaska · 8 km WSW of this epicentre
  2. 6.4 118 km E of Nikolski, Alaska · 16 km W of this epicentre
  3. 6.4 123 km ESE of Nikolski, Alaska · 24 km SW of this epicentre
  4. 6.3 136 km ESE of Nikolski, Alaska · 15 km S of this epicentre
  5. 6.3 Fox Islands, Aleutian Islands, Alaska · 28 km SW 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 52.7731, -166.8886. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.8 105 km ESE of Nikolski, Alaska
  2. 1.9 107 km E of Nikolski, Alaska
  3. 3.0 85 km SSW of Unalaska, Alaska
  4. 3.2 109 km SSW of Unalaska, Alaska
  5. 2.6 84 km S of Unalaska, Alaska
  6. 2.0 98 km E of Nikolski, Alaska
  7. 1.8 102 km E of Nikolski, Alaska
  8. 1.6 124 km S of Unalaska, Alaska
  9. 1.7 143 km S of Unalaska, Alaska
  10. 1.8 144 km S of Unalaska, Alaska
  11. 2.1 84 km S of Unalaska, Alaska
  12. 3.6 127 km S of Unalaska, Alaska
  13. 2.9 103 km ESE of Nikolski, Alaska
  14. 1.9 136 km ESE of Nikolski, Alaska
  15. 1.9 140 km ESE of Nikolski, 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.