QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8ml

93 km SW of Adak, Alaska

Yes. A magnitude 2.8 earthquake was recorded 93 km SW of Adak, Alaska at 05:51 UTC on 2019-09-18, 40 km deep.

· 40 km deep · released about 480 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 2.8 (ml)
Depth
40 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2531 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 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 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
  3. Around the size people start to feel M 3.0 2× the energy of this one
  4. This earthquake M 2.8 about 480 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 6.5 on 2018-08-15 — about 350,000 times the energy of this one.

Before 2016, the USGS record lists 176 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.9 77 km WSW of Adak, Alaska · 24 km N of this epicentre
  2. 7.3 88 km WSW of Adak, Alaska · 14 km NNW of this epicentre
  3. 7.1 60 km SW of Adak, Alaska · 35 km ENE of this epicentre
  4. 7.0 114 km WSW of Adak, Alaska · 34 km WNW of this epicentre
  5. 7.0 69 km SW of Adak, Alaska · 28 km ENE 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 51.3523, -177.6975. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.6 128 km SW of Adak, Alaska
  2. 2.2 120 km SW of Adak, Alaska
  3. 2.4 103 km WSW of Adak, Alaska
  4. 2.0 61 km SW of Adak, Alaska
  5. 2.0 115 km WSW of Adak, Alaska
  6. 1.5 113 km WSW of Adak, Alaska
  7. 1.7 76 km SW of Adak, Alaska
  8. 2.3 82 km SW of Adak, Alaska
  9. 1.8 78 km WSW of Adak, Alaska
  10. 3.0 84 km WSW of Adak, Alaska
  11. 1.5 116 km SW of Adak, Alaska
  12. 2.8 120 km SW of Adak, Alaska
  13. 1.8 114 km WSW of Adak, Alaska
  14. 1.9 125 km WSW of Adak, Alaska
  15. 2.2 134 km SW of Adak, 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.