Measurements of Acoustic Wave Propagation and Scattering in Shallow Oceans and a Sediment Scattering Model.

摘要

LONG-TERM GOAL. To better understand the physics of acoustic/elastic wave propagation and scattering in shallow oceans and sediments at frequencies between 100 Hz and 100 kHz. SCIENTIFIC OBJECTIVES. (1) To develop a universal (forward/inverse) model for the seafloor roughness scattering and the sediment volume scattering. (2) To accurately measure the propagation and scattering of acoustic waves from the sediments. (3) To determine how much of the attenuation with sediments is due to the viscosity of pore fluid, the shear wave conversion, and the scattering of acoustic waves. (4) To accurately measure sediment properties accoustically including permeability, porosity, density, compressional and shear wave velocity and attenuation. APPROACH. (1) The Yamamoto (1996) theory of sediment volume scattering will be combined with the Jackson et al. (1989) theory of seafloor roughness scattering. (2) The high angular resolution bi-linear acoustic array developed at the Geoacoustics Laboratory (GAL) will be used to separate the head waves, sediment volume scattered waves, and scattered waves from rough sea-floor from incident waves. The bistatic scattering data from FY95 and the future experiment in FY97 will be used to test models. (3) A new sediment model which includes the effect of macro-pores, and micro-pores in sediments will be developed. This theory will be tested by cross-well tomography experiments through various sediments.