QuakeIndex

Earthquake · reviewed by a seismologist

M 4.8mb

134 km SE of Akutan, Alaska

Yes. A magnitude 4.8 earthquake was recorded 134 km SE of Akutan, Alaska, at 5:31 pm AKST on 26 February 2018 (02:31 UTC), 9.0 km deep.

· 9.0 km deep · released about 240 tons 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 4.8 (mb)
Depth
9.0 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1190 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 170 km (106 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 240 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 710× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 32× the energy of this one
  3. Magna, Utah 2020 M 5.7 22× the energy of this one
  4. This earthquake M 4.8 about 240 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 500× more

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 5.1 on 2017-05-24 — about 2.8 times the energy of this one.

Before 2016, the USGS record lists 39 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.6 146 km ESE of Akutan, Alaska · 35 km NE of this epicentre
  2. 6.6 92 km SE of Akutan, Alaska · 43 km NW of this epicentre
  3. 6.2 136 km SE of Akutan, Alaska · 14 km NE of this epicentre
  4. 6.2 136 km S of False Pass, Alaska · 44 km NE of this epicentre
  5. 6.2 156 km SE of Akutan, Alaska · 22 km SE 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 53.3542, -164.2098. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.4 164 km ESE of Akutan, Alaska
  2. 2.9 155 km ESE of Akutan, Alaska
  3. 4.3 152 km ESE of Akutan, Alaska
  4. 3.9 163 km ESE of Akutan, Alaska
  5. 2.7 160 km ESE of Akutan, Alaska
  6. 2.1 160 km ESE of Akutan, Alaska
  7. 2.3 160 km ESE of Akutan, Alaska
  8. 3.6 156 km ESE of Akutan, Alaska
  9. 3.0 153 km ESE of Akutan, Alaska
  10. 2.3 158 km S of False Pass, Alaska
  11. 2.4 160 km ESE of Akutan, Alaska
  12. 2.4 160 km ESE of Akutan, Alaska
  13. 5.5 160 km ESE of Akutan, Alaska
  14. 1.9 107 km SE of Akutan, Alaska
  15. 3.5 96 km ESE of Akutan, 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.