QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

124 km W of Adak, Alaska

Yes. A magnitude 1.8 earthquake was recorded 124 km W of Adak, Alaska at 19:31 UTC on 2018-10-29, 9.7 km deep.

· 9.7 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
9.7 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1185 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 9 km (6 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 6.5 on 2018-08-15 — about 11,000,000 times the energy of this one.

Before 2016, the USGS record lists 163 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 162 km WSW of Adak, Alaska · 43 km SW of this epicentre
  2. 7.0 114 km WSW of Adak, Alaska · 30 km SE of this epicentre
  3. 7.0 148 km WSW of Adak, Alaska · 40 km SSW of this epicentre
  4. 6.9 151 km WSW of Adak, Alaska · 39 km SSW of this epicentre
  5. 6.6 152 km WSW of Adak, Alaska · 36 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 51.6816, -178.4058. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 1.8 122 km WSW of Adak, Alaska
  2. 1.8 126 km W of Adak, Alaska
  3. 1.7 119 km WSW of Adak, Alaska
  4. 2.2 100 km WSW of Adak, Alaska
  5. 1.9 130 km W of Adak, Alaska
  6. 3.0 130 km WSW of Adak, Alaska
  7. 2.3 129 km W of Adak, Alaska
  8. 2.2 129 km W of Adak, Alaska
  9. 4.3 117 km WSW of Adak, Alaska
  10. 2.7 138 km WSW of Adak, Alaska
  11. 1.9 125 km W of Adak, Alaska
  12. 2.1 105 km WSW of Adak, Alaska
  13. 1.7 106 km WSW of Adak, Alaska
  14. 1.8 152 km W of Adak, Alaska
  15. 1.8 126 km WSW 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.