New laboratory measurements of sediment properties in cores from the Bering Sea, North Sea, Mediterranean Sea, equatorial Pacific, and other areas, have been combined with older measurements and the results, with statistical analyses, are presented (for various sediment types in three general environments) in tables, diagrams, and regression equations. The measured properties are sound velocity, density, porosity, grain density, and grain size; computed properties are velocity ratios (sediment velocity/water velocity) and impedance. Mineral-grain microstructures of sediments are critical in determining density, porosity, and sound velocity; compressibility of pore water is the critical factor in determining sound velocity. New regression equations are provided for important empirical relationships between properties. Corrections of laboratory values to sea-floor values are discussed. It is concluded that sound velocity and density are about the same for a given sediment type in the same environment in any ocean if porosity is about the same. Given the mean size of mineral grains, or average porosity, of a sediment, the average sound velocity can be predicted within 1% or 2% in most environments. Comparisons with recent in situ measurements validate the laboratory measurements.

In situ sediment acoustic impedance measured from a ship underway is being used to infer the physical properties of the sea bed. These inferences rely on published regression relationships developed to estimate impedance from sediment density or porosity. Thus the equations must be rearranged to yield the desired parameter when impedance is known. Rearranging or inverting regression equations is not a valid technique. It is justified only when properly derived equations are unavailable. Herein are regressions of sediment density, porosity, and mean grain size on impedance to complement relationships already in the literature. Presented also are data and methods to place confidence limits on the predictions.

Marine sediments under overburden pressure commonly develop elastic anisotropy, probably of the transverse type with a single vertical axis of symmetry. Surface measurements of sound interval velocity in such materials, as by wide angle reflection profiling, provide a value between the vertical and horizontal velocities, thus introducing errors when measured velocity is used in determining section thickness. Empirical regression equations from laboratory measurements allow estimation of in situ vertical or horizontal velocity when one or the other is known in marine calcareous (Vv, km/s = 0.18 + 0.89Vh) and siltclay (Vv, km/s = 0.25 + 0.83 Vh) sediments and sedimentary rocks. These equations allow determination of the maximum error caused by anisotropy in section thickness determinations.

Detailed seafloor environmental modeling of a moderately complex shallow water area, coupled with multitone matched-field processing, produced reliable and unambiguous source detection and tracking. Frequency averaging of the matched-field output sufficiently reduced sidelobe ambiguities. The seabed geologic model is a gridded database containing water depth, sediment grain size, sediment thickness, and acoustic basement type. Grid cells are squares of side length equal to 2 arc s. Software, separate from the geologic model, computes a geoacoustic model for any desired grid square.

Measurements of four of the five elastic stiffnesses of marine calcareous rocks and estimates of the fifth, c•3, allow more detailed discussion of elastic wave propagation in these rocks than previously possible. The constant c• 3, which is seldom measured and was not measured in the rocks of this study, was derived by equating the Gassmann and Hashin-Shtrikman estimates of the bulk moduli of chalk and limestone and then solving for the single unknown c•3. For chalk, the measured constants, in N/m 2 x 10 •ø, are c• = 1.01, %3 = 0.94, c,•,• = 0.18, and c66 = 0.21. For limestone, the measured constants, also in N/m 2 x 10 •ø, are c• = 2.41, %3 = 2.09, c,•,• = 0.47, and c66 = 0.60. Three physically possible values orca3 were computed for chalk ( 0.48, 0.52, and 0.63 N/m 2 x 10 •ø) and for limestone (0.73, 1.05, and 1.24 N/m 2 x 10•ø). Heretofore, the only statements which could be made about c•3 in these rocks arelcfii < 0.87 x 10 •ø N/m 2 (chalk), and Ic•3 [ < 1.94 x 10 •ø N/m 2 (limestone). The calculations require the assumption that anisotropy in these rocks is caused by mineral alignment and the simplification of monomineralogy (calcite). On the basis of these measurements and estimates, the effect of elastic anisotropy on seismic reflection determinations of vertical compressional wave speed in calcareous rocks below the earth's surface is small ( + 6%), whereas similar determinations of vertically polarized shear wave speeds may be unreliable. Relationships are provided to convert seismic refraction measurements of horizontal compressional wave velocity to vertical velocity. These relationships are independent of the estimated values of c• 3-