In underwater acoustics, geophysics, and geologic studies, given a seismic measure- 

 ment of velocity, the relations between sound velocity and density allow assignment of 

 approximate values of density to sediment and rock layers of the earth's crust and mantle. 

 In the past, single curves of velocity versus density represented all sediment and rock types. 

 A large amount of recent data from the Deep Sea Drilling Project (DSDP) and reflection 

 and refraction measurements of sound velocity, allow construction of separate velocity- 

 density curves for the principal marine sediment and rock types. This report uses carefully- 

 selected data from laboratory and in situ measurements to present empirical sound velocity- 

 density relations (in the form of regression curves and equations) in terrigenous silt-clays, 

 turbidites and shale, in calcareous materials (sediments, chalk, and limestone), and in 

 siUceous materials (sediments, porcelanite and chert); a pubUshed curve for DSDP basalts 

 is included. Speculative curves are presented for composite sections of basalt and sediments. 

 These velocity-density relations, with seismic measurements of velocity, should be useful in 

 assigning approximate densities to sea floor sediment and rock layers for studies in marine 

 geophysics and in forming geoacoustic models of the sea floor for underwater acoustic 

 studies. 



PRODUCTION OF GEOACOUSTIC MODELS 



Introduction 



Geoacoustic models were defined and requirements for input information were 

 noted briefly in the general introduction to Part I (Marine Sediment Properties). As noted 

 in the general introduction, geoacoustic models of the sea floor are produced to guide 

 theoretical studies, to reconcile experiments at sea with theory, and to predict the effects 

 of the sea floor on underwater sound propagation. 



Studies From 1974 to 1977 



During the three-year period of this project, geoacoustic models were furnished to 

 various persons or groups. 



• Two geoacoustic models were furnished to the Acoustic Environmental 

 Support Detachment, ONR. One was for an area in the Northeast Pacific and was well 

 founded on coring and acoustic reflection measurements. The second model was for the 

 northern end of the Iberian Basin off the coast of Spain and was based on information 

 in the hterature. These data with accompanying bottom-loss curves were issued by the 

 Naval Undersea Center TN 1470 (Morris et al, 1974). 



• Geoacoustic models were furnished to investigators in the Undersea Surveil- 

 lance Department, Naval Undersea Center, for areas or stations in the following locahties. 



1 . Continental slope west of the Strait of Juan de Fuca 



2. Northeast Pacific: Tufts Abyssal Plain, and another area south of 

 Mendocino Escarpment 



20 



