Lehmann discontinuity explained
The Lehmann discontinuity is an abrupt increase of P-wave and S-wave velocities at the depth of 220km (140miles) in Earth's mantle, discovered by seismologist Inge Lehmann.[1] [2] [3] The thickness is 220 km . It appears beneath continents, but not usually beneath oceans,[4] and does not readily appear in globally averaged studies. Several explanations have been proposed: a lower limit to the pliable asthenosphere, a phase transition,[5] and most plausibly, depth variation in the shear wave anisotropy.[6]
Notes
- Book: Fundamentals of geophysics . William Lowrie . 158 . 0-521-46728-4 . 1997 . Cambridge University Press.
- Lehmann, I. (1936): P', Publications du Bureau Central Seismologique International, Série A, Travaux Scientifique, 14, 87–115.
- Web site: Martina Kölbl-Ebert . Inge Lehmann's paper: " P' " (1936) . December 2001.
- 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. . Mineralogy and elasticity of the oceanic upper mantle: Origin of the low-velocity zone . Lars Stixrude and Carolina Lithgow-Bertolloni . J. Geophys. Res. . 110 . 10.1029/2004JB002965 . 2005 . B3 . B03204 . 2005JGRB..110.3204S . free . 2027.42/94924 . free .
- Book: Plate tectonics and crustal evolution . Kent C. Condie . 123 . 0-7506-3386-7 . . 1997 . 4th.
- Book: Vertical coupling and decoupling in the lithosphere; Volume 227 of special publications . 14 . https://books.google.com/books?id=SBs3o5uWeicC&pg=PA14 . MK Savage, KM Fischer CE Hall . Strain modelling, seismic anisotropy and coupling at strike-slip boundaries... . John Gocott . 1-86239-159-9 . . 2004.
General references
- Book: Advances in geophysics, Volume 12 . P. Caloi . H. E. Landsberg, J. Van Mieghem . https://books.google.com/books?id=_z2uoqkaHAIC&pg=PA167 . 167 ff . 0-12-018812-0 . 1967 . . The “20° Discontinuity”. – some historic background.
Further reading
Book: Deformation of earth materials: an introduction to the rheology of solid earth . Shun-ichirō Karato . 318 . 978-0-521-84404-8 . 2008 . Cambridge University Press.
External links
