The Normally-Incident Reflectivity of the Sea Floor at 12 KC and Its Correlation with Physical and Geological Properties of Naturally-Occurring Sediments

摘要

The objective of this investigation was to measure bottom loss in normal incident reflection of pulses of 12 kcps sound and to study its geological significance. A semi-automatic instrument system was developed capable of making continuous measurements of the peak pressure and the time integral of the square of the pressure of the sea-floor echo from a vessel underway. Observations were taken in both deep and shallow water in the Western North Atlantic. The early cruises were conducted in deep water to investigate the range and variability of bottom loss. Geological control consisted mainly of a precise bathymetric record. Later cruises were conducted in shallow water where the geology had been well studied previously. In these latter cruises the acoustic measurements were correlated with sediment dredging and underwater photography. Thirty-one thousand acoustic measurements were made. Median bottom loss values and standard deviations were computed and the results summarized in eleven hundred sets, each set corresponding with a location at sea. Seventy-seven sediment stations were occupied. A complete particle size analysis and a water content analysis were performed on these sediments to determine their size and mass characteristics. (Author)