ON THE PHASE SPEED AND ATTENUATION OF AN INTERFACE WAVE IN AN UNCONSOLIDATED MARINE SEDIMENT

The phase speed and attenuation of the interface wave at the seawater–sediment boundary are obtained by solving the characteristic equation for one of its complex roots. The characteristic equation itself is derived on the basis of a recently developed theory of wave propagation in porous media. Central to the theory is the stress relaxation that occurs when mineral grains slide against one another during the passage of a seismic wave. This type of stress relaxation is characterized by material response functions for compressional and shear waves of the form h(t)∝t−n, where t is time since the sliding began and n is a small positive number. The phase speed of the interface wave relative to that of the shear wave depends weakly on the grain size, increasing from about 85% for fine-grained silts and clays to 90% for coarse sands. The loss tangent of the interface wave, βi, is found to be independent of the mechanical properties (grain size, porosity, and density) of the sediment, and is the same as that for...

[1]  W. L. Roever,et al.  Propagation of elastic wave motion from an impulsive source along a fluid/solid interface , 1959, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[2]  Richard K. Johnson,et al.  Laboratory measurements of shear wave attenuation in saturated sand , 1980 .

[3]  J. Dorman,et al.  Seismic study of the sediments in the Hudson River , 1968 .

[4]  O. K. Rice.  On the Statistical Mechanics of Liquids, and the Gas of Hard Elastic Spheres , 1944 .

[5]  M. Buckingham.  Theory of compressional and transverse wave propagation in consolidated porous media , 1999 .

[6]  E. Hamilton.  Compressional-wave attenuation in marine sediments , 1972 .

[7]  D. Rauch.  On the Role of Bottom Interface Waves in Ocean Seismo-Acoustics: A Review , 1986 .

[8]  Use of Stoneley Waves to Determine the Shear Velocity in Ocean Sediments , 1964 .

[9]  D. Chapman,et al.  A Summary of DREA Observations of Interface Waves at the Seabed , 1991 .

[10]  D. Rauch.  Experimental and Theoretical Studies of Seismic Interface Waves in Coastal Waters , 1980 .

[11]  M. Buckingham.  Theory of acoustic attenuation, dispersion, and pulse propagation in unconsolidated granular materials including marine sediments , 1997 .

[12]  Michael J. Buckingham,et al.  Theory of compressional and shear waves in fluidlike marine sediments , 1998 .

[13]  G. Nolet,et al.  Waveform analysis of Scholte modes in ocean sediment layers , 1996 .

[14]  F. Schirmer.  Experimental Determination of Properties of the Scholte Wave in the Bottom of the North Sea , 1980 .

[15]  D. Davies.  Dispersed stoneley waves on the ocean bottom , 1965 .

[16]  H. P. Bucker,et al.  VELOCITIES OF COMPRESSIONAL AND SHEAR WAVES IN MARINE SEDIMENTS DETERMINED IN SITU FROM A RESEARCH SUBMERSIBLE , 1970 .

[17]  Loyd D. Hampton,et al.  Acoustic Properties of Sediments , 1964 .

[18]  K. Graff.  Wave Motion in Elastic Solids , 1975 .