Summary of marine sedimentary shear modulus and acoustic speed profile results using a gravity wave inversion technique

Abstract

Experimental techniques and inverse methods have been established to extract marine sediment shear modulus with depth profiles from measurements of wave-induced seabed motion on the shallow continental shelf. Seabed sediments are modeled as a quasistatic, incompressible, layered elastic medium in response to wave-induced pressures. An iterative eigenvalue expansion technique is used to extract the inverse. Under typical continental shelf conditions, this inversion method is found to have a depth resolution limit of approximately 3 m, with a maximum penetration of 200 m. Using semiempirical sediment models, it is possible to deduce sediment porosity, bulk density, and shear and compressional wave speeds from the shear modulus profile. One representative result from the New Jersey Shelf is examined in detail, and favorably compared with independent sediment profiling methods. A summary of experimentally determined sediment profiles from four other sites on the Eastern U.S. continental shelf is given.