ANDERSON: BOTTOM PROPERTIES FOR LONG-RANGE PROPAGATION PREDICTION 



Dr. A. L. Anderson: I think there are two significant points. 

 One is, as I pointed out, this calculation was made for a model with- 

 out gradients, so we need to remember that, although it is not 

 particularly germane to your point. Also, I think that you may very 

 well have a good, if not the only, way of actually measuring attenu- 

 ation at a given frequency in the sediments. 



Dr. D. C. Stickler (Applied Research Laboratory, Pennsylvania 

 State University) : I would like to point out that in your models of 

 plane-wave reflection coefficients, your layer media, that some of 

 those same effects can be observed even without the layering. 



If you consider the full effect of a point source in the iso- 

 velocity half space and higher speed bottom, you can observe some of 

 these oscillations away from the grazing angle and the breakaway from 

 the dB loss above the line. 



Dr. A. L. Anderson: Precisely, which says you must consider 

 something other than a plane-wave reflection coefficient. 



Dr. D. C. Stickler: Yes. If you do the full-wave solution for 

 a point source in isovelocity halfspace over a higher speed iso- 

 velocity halfspace and examine just the reflected field, then these 

 oscillations above grazing are present and the breakaway from the 

 zero reflection coefficient is also observed and is not related to 

 layering at all and is also frequency-dependent. 



Dr. W. H. Munk (Institute of Geophysics and Planetary Physics, 

 University of California at San Diego): Question based on ignorance. 

 Are there good statistical models of the sea bottom? And, I mean it 

 in the sense of existing statistical models of the sea surface that 

 I am familiar with which have indicated that scattering from an 

 angle of incidence steeper than the root mean square slope behaves 



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