FUNCTIONAL RELATIONSHIPS BETWEEN ACOUSTIC AND SEDIMENTOLOGICAL SEDIMENT PROPERTIES

摘要

Past works starting in the fifties have focused on both the fundamental and the empirical studies of sound propagation along porous media in general and sedimentary deposits in particular. The technique of remote sensing by means of acoustic measurements to indirectly observe the characteristics of porous, fluid saturated layers, constitutes an excellent option for the fast and nondestructive evaluation of these layers. Especially the marine sedimentary environments have been dedicated great concern to, not only for scientific reasons oriented towards a fundamental understanding of the Earth in general but also because of economical implications in a number of ways (fisheries, mineral resources, navigational routes, harbor development,...) and because of the great importance of this environment for man's quality of live. Previously, it is shown in [1] that viscoelastic models are suited for modeling the wave propagation through fine sediments. Absorption and dispersion curves were retrieved by applying a system identification technique in the frequency domain. Now, the viscoelastic modeling method will be compared with two other principal modeling methods: the model of Biot, which describes the wave propagation by a theory using mechanics of porous media, and the more recent Buckingham's model, where the sediment is considered as a bulk fluid in which grain-to-grain contacts dominate the internal losses. The main difference between these models and the viscoelastic model resides in the fact that viscoelastic models remain vague about the actual dissipation mechanisms in the sediment, while Buckingham's and Biot's model try to identify the main dissipation mechanisms and link the acoustical properties to the sedimentological sediment properties.