Open AccessSOME CONSEQUENCE OF THE EXISTENCE OF LOW-VELOCITY LAYERS
Author(s) -
Markus Båth
Publication year - 2012
Publication title -
annals of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 60
eISSN - 2037-416X
pISSN - 1593-5213
DOI - 10.4401/ag-5615
Subject(s) - core (optical fiber) , radius , inner core , layer (electronics) , geology , geodesy , physics , geophysics , optics , materials science , computer security , computer science , composite material
The velocities of elastic waves (P and S) generally increase with
depth in the earth. If at some depth this increase is replaced by a decrease
over an interval of depth, again followed by an increase at some
greater depth, we have, what we cali a low-velocity layer, provided
the numerical value of the velocity decrease with depth in at least a
part of the layer surpasses the criticai value v/r (v = velocity, r = radius;
see Gutenberg, 1954 b, and Bullen, 1954, pp. 87-89). The most
marked low-velocity layer (for P waves) exists on the inner side of the
outer core. This low-velocity layer has already been recognized by ali
seismologists long ago. If a low-velocity layer exists also at the boundary
of the inner core, is not yet certain. According to Jeffreys there is one,
whereas Gutenberg does not find suffìcient observational support for it
depth in the earth. If at some depth this increase is replaced by a decrease
over an interval of depth, again followed by an increase at some
greater depth, we have, what we cali a low-velocity layer, provided
the numerical value of the velocity decrease with depth in at least a
part of the layer surpasses the criticai value v/r (v = velocity, r = radius;
see Gutenberg, 1954 b, and Bullen, 1954, pp. 87-89). The most
marked low-velocity layer (for P waves) exists on the inner side of the
outer core. This low-velocity layer has already been recognized by ali
seismologists long ago. If a low-velocity layer exists also at the boundary
of the inner core, is not yet certain. According to Jeffreys there is one,
whereas Gutenberg does not find suffìcient observational support for it