Open AccessA Weak Layer in the Mantle? *
Author(s) -
Hales A. L.
Publication year - 1937
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1937.tb07122.x
Subject(s) - mantle (geology) , crust , geology , geophysics , scattering , square root , mechanics , physics , geometry , optics , mathematics
Summary The paper discusses the effect of a weak layer in the upper mantle on the deformation of the crust arising from atmospheric loading, and on the isostatic compensation process. It also points out that S phases with periods of I second are much more strongly damped than S phases with periods of 10 seconds or more, and than P phases with short periods. The damping arising from a liquid layer is proportional to the square root of the frequency and does not provide a satisfactory explanation. Scattering of the kind suggested by Jeffreys, or any other mechanism leading to the firmoviscous law, gives rise to damping proportional to the square of the frequency and is sufficiently frequency sensitive to be consistent with the observations. The differences between P and S can only be accounted for in terms of different behaviour of the elastic constants for dilatational and distortional movements.