Abstract:

The prediction of low- to midfrequency shallow-water reverberation is still in its infancy. This is due, in large part, to the unpredictability of the bottom-scattering kernel, and particularly, its dependence upon frequency. The bottom-scattering kernel is difficult to measure directly and even more problematic to extract from the reverberation. An experiment was conducted in a complex shallow-water area to test novel coherent and incoherent direct-path bottom-scatter measurement techniques (400--4000 Hz). Advantages and disadvantages of each technique are discussed. Analyses of the bottom-scatter data in conjunction with collocated bottom loss and high-resolution seismic data shed light on the underlying mechanisms (e.g., interface roughness, sub-bottom volume inhomogeneities, or basement roughness) that give rise to the scattering. It is hypothesized that the frequency dependence of the scattering kernel can be linked to the dominant scattering mechanism.