Variation with depth in shallow and deep water marine sediments of
porosity, density and the velocities of compressional and shear waves
Geophysics, 22 (3):
523--713 (Jul 1, 1957)DOI: 10.1190/1.1438386
Abstract
In a study of the dependence of the velocity of compressional waves
in marine sediments upon the thickness of overburden, the velocity-depth
relationship in shelf sediments is shown to be distinctly different
from that in deep basin sediments. The difference between the two
cases may be illustrated by comparing the straight lines that best
represent the data. These areEquationwhere V is in km/sec and Z is
in kilometers. Shallow and deep water are defined arbitrarily to
be under 100 fathoms and over 1,500 fathoms respectively.The observed
variation of average compressional velocity in the shallow and deep
water sediments, taken together with the known limited range of variation
of velocity for a given porosity, yields limits in turn upon the
porosity-depth dependence in the two environments. It is shown that
at the same depth of overburden porosity is much greater in deep
water sediments than in shallow.A physical argument is presented
to show that there is implicit in the observed narrow range of variation
of velocity with porosity a simple relation between porosity and
rigidity. Thus quantitative estimates of shear velocity may be made
from compressional velocity alone. In this way the original data
are used to place rather narrow limits on the depth variation of
shear velocity, porosity, and density. A number of comparisons with
observation are employed to test the conclusions at each stage of
the discussion.