QuakeIndex

Earthquake · reviewed by a seismologist

M 4.9mb

137 km WSW of Adak, Alaska

Yes. A magnitude 4.9 earthquake was recorded 137 km WSW of Adak, Alaska at 19:53 UTC on 2017-05-08, 10 km deep.

· 10 km deep · released about 340 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 4.9 (mb)
Depth
10 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1656 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 181 km (112 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 340 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 500× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 22× the energy of this one
  3. Magna, Utah 2020 M 5.7 16× the energy of this one
  4. This earthquake M 4.9 about 340 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 710× 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 6.2 on 2017-05-08 — about 89 times the energy of this one.

Before 2016, the USGS record lists 175 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 162 km WSW of Adak, Alaska · 31 km SW of this epicentre
  2. 7.0 114 km WSW of Adak, Alaska · 35 km ESE of this epicentre
  3. 7.0 148 km WSW of Adak, Alaska · 32 km S of this epicentre
  4. 6.9 151 km WSW of Adak, Alaska · 29 km SSW of this epicentre
  5. 6.8 177 km WSW of Adak, Alaska · 47 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 51.6280, -178.5839. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 2.8 126 km WSW of Adak, Alaska
  2. 3.3 130 km W of Adak, Alaska
  3. 4.6 129 km WSW of Adak, Alaska
  4. 4.6 129 km W of Adak, Alaska
  5. 3.7 129 km WSW of Adak, Alaska
  6. 2.3 127 km WSW of Adak, Alaska
  7. 2.5 133 km WSW of Adak, Alaska
  8. 3.3 127 km WSW of Adak, Alaska
  9. 2.6 131 km WSW of Adak, Alaska
  10. 2.8 125 km WSW of Adak, Alaska
  11. 3.1 128 km WSW of Adak, Alaska
  12. 3.5 134 km WSW of Adak, Alaska
  13. 2.7 133 km WSW of Adak, Alaska
  14. 3.2 122 km WSW of Adak, Alaska
  15. 3.1 122 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.