CLUTTER ON THE MALTA PLATEAU

Abstract: Acoustic and environmental measurements along a particular track on the Malta Plateau, Mediterranean Sea, are of interest for presentation in this paper because high scattering strength and reverberation deviation is persistently observed from a confined location on the Plateau. The diffuse reverberation and clutter data were acquired by a towed source and towed cardioid array with the source transmitting 1-s linear frequency modulated sweeps in the band from 800-1800 Hz every minute along the track. The received signals were acquired for 55 s to cover a large area. Environmental surveys (multibeam echo-sounder, sub-bottom profiling, side scan sonar, wide-angle reflection measurements) were conducted at this strong scattering location with no clear indication of significant scattering features, i.e. no evidence of bathymetric features, variations in sub-bottom stratification or changes in bottom geoacoustic properties. However, the sub-bottom profiling shows inclusions in the upper 5 m of the sediment which have not been detected by any of the other survey techniques. It is hypothesized that these inclusions have slightly different geoacoustic properties than the surroundings which results in strong clutter-like backscattering. This hypothesis is presented and verified by backscattered time-series computations using a two-way prediction model applied in an environment similar to that of the acquired acoustic data