GEOACOUSTIC MODEL NO. 1: 

 THE SHALLOW BERING SEA 



During July and August 1960, the Navy Electronics 

 Laboratory conducted an expedition to the Bering and Chuk- 

 chi Seas, primarily to support long-range, shallow-water 

 acoustic studies to be made in the same area several weeks 

 later under the direction of K. V. Mackenzie, then of the 

 NEL Underwater Sound Propagation Branch. The trip was 

 made aboard the Scripps Research Vessel HUGH M. SMITH, 

 which was leased to NEL for the expedition. 



During the expedition, radio transmissions were 

 made to the Mackenzie party (at sea, but three weeks be- 

 hind) concerning sediments and sediment thicknesses over 

 prominent reflectors. This information was provided to 

 permit the group to shift their experimental work if the sea- 

 floor environment was not suitable for their purposes. 

 Transmissions were made using a specially devised, pre- 

 arranged code which is reproduced in Appendix B for those 

 interested in a similar procedure; it is a useful example of 

 transmission of environmental information by radio along a 

 pre-planned track. 



Field Program 



The program of the expedition is outlined as follows. 



1. GEOLOGIC STUDIES 



a. The thicknesses of sediments, layering in the 

 sediments, and the structure of rock beneath the sediments 

 on the shallow-water portions of the continental shelf were 

 the most important of the various studies. Two techniques 

 were used. The Marine Sonoprobe operating between 4 and 

 8 kc/s, and the "Arcer" operating between 200 and 500 c/s, 

 covered approximately 90 percent of the track. In general, 

 there were 5 to 50 feet of sediment overlying the first 

 prominent reflector (thought to be rock) in the Bering Sea. 



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