QuakeIndex

Earthquake · reviewed by a seismologist

M 2.3ml

149 km S of Adak, Alaska

Yes. A magnitude 2.3 earthquake was recorded 149 km S of Adak, Alaska at 17:25 UTC on 2018-09-12, 4.7 km deep.

· 4.7 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
4.7 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 7 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2539 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 5.3 on 2017-05-09 — about 32,000 times the energy of this one.

Before 2016, the USGS record lists 12 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.4 146 km S of Adak, Alaska · 19 km WNW of this epicentre
  2. 6.1 189 km S of Adak, Alaska · 50 km SW of this epicentre
  3. 6.0 136 km S of Adak, Alaska · 31 km WNW of this epicentre
  4. 5.8 176 km S of Adak, Alaska · 34 km SW of this epicentre
  5. 5.8 164 km S of Adak, Alaska · 20 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 50.5326, -176.5656. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.8 100 km S of Adak, Alaska
  2. 2.5 112 km S of Adak, Alaska
  3. 1.7 107 km SSE of Adak, Alaska
  4. 1.9 102 km S of Adak, Alaska
  5. 1.8 105 km S of Adak, Alaska
  6. 1.9 103 km S of Adak, Alaska
  7. 2.8 113 km S of Adak, Alaska
  8. 1.8 103 km S of Adak, Alaska
  9. 3.0 110 km SSE of Adak, Alaska
  10. 3.9 106 km S of Adak, Alaska
  11. 2.5 116 km S of Adak, Alaska
  12. 3.6 105 km S of Adak, Alaska
  13. 2.5 111 km S of Adak, Alaska
  14. 3.5 107 km S of Adak, Alaska
  15. 3.1 109 km S 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.