This article is about a discontinuity in Earth's mantle. For the discontinuity in the core, see inner core
||This article needs attention from an expert on the subject. (December 2008)
Velocity of seismic S
-waves in the Earth near the surface in three tectonic provinces: TNA= Tectonic North America SNA= Shield North America & ATL = North Atlantic.
The Lehmann discontinuity refers to an abrupt increase of P-wave and S-wave velocities in the vicinity of 220±30 km depth, discovered by seismologist Inge Lehmann. It appears beneath 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 aesthenosphere, a phase transition, and most plausibly, depth-variation in the shear wave anisotropy. Further discussion of the Lehmann discontinuity is found in Karato.
- ^ Figure patterned after Don L Anderson (2007). New theory of the earth (2nd ed.). Cambridge University Press. p. 102, Figure 8.6. ISBN 0-521-84959-4.; Original figure attributed to Grand & Helmberger (1984)
- ^ The thickness is 220 km. William Lowrie (1997). Fundamentals of geophysics. Cambridge University Press. p. 158. 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). Plate tectonics and crustal evolution (4rth ed.). Butterworth-Heinemann. p. 123. 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. Vertical coupling and decoupling in the lithosphere; Volume 227 of special publications. Geological Society. p. 14. ISBN 1-86239-159-9.
- ^ Shunʼichirō Karato (2008). Deformation of earth materials: an introduction to the rheology of solid earth. Cambridge University Press. p. 318. ISBN 0-521-84404-5.
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