QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

167 km S of Adak, Alaska

Yes. A magnitude 1.8 earthquake was recorded 167 km S of Adak, Alaska at 15:34 UTC on 2024-06-20, 4.9 km deep.

· 4.9 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
4.9 km below the surface
Felt
no reports yet
Nearest mapped fault
Alaska-Aleutian subduction zone, 12 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 836 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 13 km (8 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 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 2016-11-29 — about 22,000 times the energy of this one.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.4 146 km S of Adak, Alaska · 47 km WNW of this epicentre
  2. 6.3 159 km SSE of Adak, Alaska · 45 km ENE of this epicentre
  3. 5.8 176 km S of Adak, Alaska · 46 km WSW of this epicentre
  4. 5.8 164 km S of Adak, Alaska · 36 km W of this epicentre
  5. 5.7 Andreanof Islands, Aleutian Islands, Alaska · 25 km S 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 50.3913, -176.2306. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.5 131 km S of Adak, Alaska
  2. 4.2 167 km S of Adak, Alaska
  3. 2.6 168 km S of Adak, Alaska
  4. 2.2 156 km S of Adak, Alaska
  5. 2.5 173 km SSE of Adak, Alaska
  6. 2.4 147 km SSE of Adak, Alaska
  7. 2.8 153 km S of Adak, Alaska
  8. 2.5 145 km S of Adak, Alaska
  9. 2.8 136 km SSE of Adak, Alaska
  10. 2.9 169 km S of Adak, Alaska
  11. 2.7 143 km S of Adak, Alaska
  12. 2.5 188 km SSE of Adak, Alaska
  13. 2.5 145 km S of Adak, Alaska
  14. 3.4 138 km SSE of Adak, Alaska
  15. 2.0 171 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.