2. Forty-seven selected in situ measurements of shear wave velocity in 

 silt-clays and turbidites to 650 meter depth yielded three regression equations. The 

 equation for the to 40 meter depth interval (Vg =116 + 4.65D) indicates the gradient 

 (4.65 sec~l) to be four to five times greater than for compressional waves in this interval. 

 At greater depths the gradients are comparable. 



3. These findings will facihtate prediction of shear wave velocity profiles 

 and gradients. 



• The attenuation of shear waves was studied and methods of prediction were 

 outlined. 



• Studies were completed which allowed construction of separate velocity versus 

 density curves and equations for the common sediment and sedimentary rock types. This 

 will allow prediction of density given a velocity from a sediment or rock layer (as from a 

 sonobuoy measurement). 



• There is now enough information on sediment properties to predict a reason- 

 able geoacoustic model once an acoustic reflection survey is given for an area. This was 

 done for several areas in the Indian, Pacific, and Atlantic Oceans. However, more work 

 needs to be done in several categories to facilitate and improve such predictions (see 

 Recommendations). 



• A general purpose plane wave reflection model has been developed that can 

 account for both liquid and/or solid layers. Computer calculations are efficient and 

 accurate. 



• A technique was developed to couple a bottom loss model to the Parabolic 

 Equation (P.E.) sound propagation model. 



RECOMMENDATIONS 



Continuous Reflection Profiling and Associated Matters 



• General statement 



Measurements from continuous reflection profiling allow delineation of sedi- 

 ment and rock layers, their true thicknesses, their interval or mean velocities, and velocity gra- 

 dients. Continuous acoustic reflection profiling was largely developed in Navy laboratories and 

 in academic and research institutions supported by the Navy. When the utihty of this 

 technique for off-shore oil exploration became evident, there was a flash evolution to 

 present-day techniques involving extremely expensive, multichannel, long-array equip- 

 ment, and very expensive data processing at sea and ashore. The oceanographic institu- 

 tions have entered this newer technology, but the costs inhibit progress. Ways need to be 

 found to reduce costs (or acquire the money) and to simplify equipment and processing 

 so that Navy-supported ships in the laboratories, academic and research institutions and 

 the Naval Oceanographic Office (NAVOCEANO) can use the modem technology. 



