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 are [Formula: see text] shallow water, [Formula: see text] deep water where 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.

of the same kind, the method of calculating matrix elements developed in reference 1 is applicable. The calculations are tedious, however, and the resulting expression for the energy in terms of cx, P, and c is rather complicated. Minimization of the energy leads to an optimum value for the binding energy of roughly 0.135 ev, when O. =P = (0.5)& an/ c = 0.052, approximately.

The relationship between the sound velocity and density in various oxide compounds at atmospheric pressure is relevant to problems of the earth's interior. Here, data on elastic constants of various compounds are collected and analyzed. It is shown that the bulk modulus‐volume per ion pair relationship for oxide compounds differs in a remarkable degree from that found for alkali halides, fluorides, selenides, sulfides, and covalent compounds. It is shown that a change of volume has the same effect on the bulk modulus of oxide compounds, whether the volume change is produced by pressure, compositional variation, phase changes, temperature, or porosity. It thus appears that volume is the primary variable affecting the elastic moduli of oxide compounds, and all other variables affect the moduli only insofar as they affect the volume itself.

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A sonic pulse system, similar to that used at Lamont Geological Observatory for seismic model experiments, was used aboard the Research Vessel VEMA during the summer of 1954 to determine high frequency seismic velocities in fresh deep sea sediment cores. Velocity profiles were obtained from 26 cores covering a wide range of lithologies and ages (Recent to Miocene). Density, porosity, median grain size, sorting, carbonate content, and salt content were also measured. The compressional wave velocity in the ocean‐bottom unconsolidated sediments studied is well represented by the equation: [Formula: see text] where v′=compressional wave velocity in km/sec ϕ=median grain size in phi units γ=percentage of HCl soluble material η=porosity. Many measurements gave velocities less than the velocity of sound in sea water. Most of the low carbonate samples followed a velocity‐porosity relation given by the Wood (1941) equation. The regression coefficient, −.44η, agrees well with the average slope of the Wood equation over the observed porosity range. High carbonate and large median grain size samples gave velocities above that predicted by the Wood equation. These higher velocities are explained as the combined result of shear strength and low effective porosity in the samples. The highest velocities were found in slowly deposited sediments. The degrees of sorting of the sediments had no observable effect on the seismic velocities except that unexplained variations were greater for more poorly sorted materials. No correlation between velocity and age was evident in the sediments studied. The effect of temperature, between 40 and 80°F. on compressional velocity in sediments may be explained by changes in elastic properties of the water fraction alone. The effect of compaction in the upper 15 or 20 feet of homogeneous sediments produced a change in seismic velocity not greater than 1 or 2 percent. Attenuation was greater in the coarse‐grained high‐velocity sediments than in sediments of smaller grain size.