Estimates of sediment volume heterogeneity spectra from several distinct shallow water locations

Abstract

Theory indicates that sediment volume heterogeneities tend to dominate seabed scattering above the critical angle. However, recent evidence indicates that scattering from volume heterogeneities can also be the dominant mechanism below the critical angle. This raises questions about the nature and scales of volume heterogeneities in marine sediments. Direct measurements of sediment heterogeneities have been performed on cores using for example x-ray CT scans, however this and related methods only sample a very small volume. In this paper, a method is presented for estimating sediment heterogeneity spectra from acoustic reverberation data where the sediment volume probed is order 107 m3. The large averaging volume permits measuring a wide range of spatial frequencies and tends to emphasize persistent scales. Resulting sediment volume spectra from several different shallow water regions will be presented. [Research sponsored by the ONR Ocean Acoustics.]