QuakeIndex

Earthquake · reviewed by a seismologist

M 2.7ml

137 km S of Unalaska, Alaska

Yes. A magnitude 2.7 earthquake was recorded 137 km S of Unalaska, Alaska, at 11:32 pm AKDT on 21 October 2024 (07:32 UTC), 19 km deep.

· 19 km deep · released about 340 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 2.7 (ml)
Depth
19 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 678 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, people at rest would likely notice it out to about 16 km (10 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 340 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 45,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 32,000× the energy of this one
  3. Around the size people start to feel M 3.0 2.8× the energy of this one
  4. This earthquake M 2.7 about 340 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 5.9 on 2017-05-24 — about 63,000 times the energy of this one.

Before 2016, the USGS record lists 43 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 127 km E of Nikolski, Alaska · 23 km WNW of this epicentre
  2. 6.4 118 km E of Nikolski, Alaska · 31 km WNW of this epicentre
  3. 6.4 123 km ESE of Nikolski, Alaska · 28 km W of this epicentre
  4. 6.3 136 km ESE of Nikolski, Alaska · 13 km W of this epicentre
  5. 6.3 Fox Islands, Aleutian Islands, Alaska · 36 km W 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 52.6422, -166.7093. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.8 136 km S of Unalaska, Alaska
  2. 3.3 135 km S of Unalaska, Alaska
  3. 3.3 136 km S of Unalaska, Alaska
  4. 2.4 115 km S of Unalaska, Alaska
  5. 2.6 136 km S of Unalaska, Alaska
  6. 2.9 132 km S of Unalaska, Alaska
  7. 2.7 119 km S of Unalaska, Alaska
  8. 2.4 128 km S of Unalaska, Alaska
  9. 2.9 132 km S of Unalaska, Alaska
  10. 2.6 133 km S of Unalaska, Alaska
  11. 3.6 114 km S of Unalaska, Alaska
  12. 2.4 138 km S of Unalaska, Alaska
  13. 3.0 122 km S of Unalaska, Alaska
  14. 2.9 128 km S of Unalaska, Alaska
  15. 3.5 136 km S of Unalaska, 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.