This article is about a discontinuity in Earth's mantle. For the discontinuity in the core, see
Velocity of seismic
-waves in the Earth near the surface in three tectonic provinces: TNA = Tectonic North America SNA = Shield North America and ATL = North Atlantic.
Lehmann discontinuity refers to an abrupt increase of and P-wave velocities at the depth of 220±30 km, discovered by S-wave seismologist Inge Lehmann. It appears beneath [2 ] continents, but not usually beneath oceans, and does not readily appear in globally averaged studies. Several explanations have been proposed; a lower limit to the pliable [3 ] asthenosphere, a phase transition, and most plausibly, depth-variation in the [4 ] shear wave anisotropy. Further discussion of the Lehmann discontinuity is found in Karato. [5 ] [6 ]
^ Figure patterned after Don L Anderson (2007). (2nd ed.). Cambridge University Press. p. 102, Figure 8.6. New Theory of the Earth ISBN 0-521-84959-4. ; Original figure attributed to Grand and Helmberger (1984)
^ The thickness is 220 km. William Lowrie (1997). . Cambridge University Press. p. 158. Fundamentals of geophysics ISBN 0-521-46728-4.
^ Lars Stixrude and Carolina Lithgow-Bertolloni (2005). "Mineralogy and elasticity of the oceanic upper mantle: Origin of the low-velocity zone". J Geophys. Res. 110: B03204. doi: 10.1029/2004JB002965. The first possible explanation is that the Lehmann is not a global feature...the Lehmann is more prevalent under continents and may be absent under all or most of the oceans.
^ Kent C. Condie (1997). (4th ed.). Butterworth-Heinemann. p. 123. Plate tectonics and crustal evolution ISBN 0-7506-3386-7.
^ MK Savage, KM Fischer CE Hall (2004). "Strain modelling, seismic anisotropy and coupling at strike-slip boundaries...". In John Gocott. . Geological Society. p. 14. Vertical coupling and decoupling in the lithosphere; Volume 227 of special publications ISBN 1-86239-159-9.
^ Shunʼichirō Karato (2008). . Cambridge University Press. p. 318. Deformation of earth materials: an introduction to the rheology of solid earth ISBN 0-521-84404-5.
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