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Lehmann discontinuity

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Title: Lehmann discontinuity  
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Lehmann discontinuity

Velocity of seismic S-waves in the Earth near the surface in three tectonic provinces: TNA = Tectonic North America SNA = Shield North America and ATL = North Atlantic.[1]

The Lehmann discontinuity is an abrupt increase of P-wave and S-wave velocities at the depth of 220±30 km, discovered by seismologist Inge Lehmann.[2] It appears beneath continents, but not usually beneath oceans,[3] and does not readily appear in globally averaged studies. Several explanations have been proposed: a lower limit to the pliable asthenosphere, a phase transition,[4] and most plausibly, depth variation in the shear wave anisotropy.[5] Further discussion of the Lehmann discontinuity can be found in the book Deformation of Earth Materials by Shun-ichirō Karato.[6]

Notes

  1. ^ Figure patterned after ; Original figure attributed to Grand and Helmberger (1984)
  2. ^ The thickness is 220 km.
  3. ^
  4. ^
  5. ^
  6. ^

General references

  • – some historic background.

External links

  • Inge Lehmann, UCLA
  • Career highlights of Inge Lehmann from UCLA


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