SECT. 3] 



PHYSICAL PROPERTIES OF MARINE SEDIMENTS 



2. Relationships among Observables 



795 



The physical properties to be dealt with in this chapter are listed in Table I, 

 together with the symbols and units employed. Observables that specify 

 particle statistics or sediment type have been omitted from the table but some 

 will be discussed later in connection with results. Also omitted are observables 

 that are not properties of the sediments alone. The group velocity of a dispersed 

 wave in shallow water, for example, depends to some extent upon the density 

 and elastic properties but it is especially a characteristic of a particular depth 

 variation of these quantities. Heat flow is not a property of the sediments at all 

 except to the extent that sources within the sediments might contribute to the 

 total flow. 



Equations relating physical properties that make possible the computation 

 or estimation of one quantity from measured values of others are given in 

 Table II. Some are generally valid both for sediments and sedimentary rocks; 



Table I 



others are valid only in limiting cases. Those equations that are strictly valid 

 only for isotropic elastic media may, when applied to porous media, be con- 

 sidered to define dynamic values of such quantities as k, /x, ct and E. 



A marine sediment is a particle aggregate with the interstices completely 

 water-filled. A number of theoretical discussions of these porous or granular 

 media have been reported. The reader is referred to papers of Anient (1953), 

 Biot (1956. 1956a), Zwikker and Kosten (1949), Gassman (1951) and Paterson 

 (1956) for information on their elastic behavior. Parasnis ( 1 960) has computed the 

 thermal conductivity to be expected under certain special assumptions with 

 regard to grain shape. Porous media are in general neither isotropic nor per- 

 fectly elastic. Even when isotropic on a scale large compared with grain sizes, 

 two dilatational waves and one rotational wave, each with a different velocity, 

 can occur. Both attenuation and the velocities have been shown to increase 



