Variability in normal-incidence acoustic response in shallow-water marine sediments

Due to several processes, lateral deviations in geotechnical properties of sediments occur at many spatial scales and in all types of sediments. These deviations influence sediment bulk elasticity and density and determine the degree and type of acoustic response. Small changes in one or more properties can produce a wide variation in the acoustic response and empirical curve fitting most often serves as models for these relationships. Sedimentary data and acoustic variability at 30 and 50 kHz from three sites in the Mississippi Sound [Lambert et al., Mar. Geol. 182 (2002)] have been further analyzed and compared with the available Shepard's sediment classes. Initial observations revealed trends in sediment variability that affect the accuracy of sediment classifications based on acoustic response. This analysis deviates from traditional sediment classification schemes and utilized hierarchical clustering with user-selected combinations of geotechnical parameters to group individual sediment samples. The sediment properties are correlated with the acoustic coefficient of variation of the ensemble-averaged acoustic response and with the group-averaged acoustic response. The variability of sediment properties and acoustic response show varying degrees of correlation between parameters of major and minor importance.