Johan O. A. Robertsson
Alan Levander
Dept. of Geol. and Geophys., Rice Univ., P.O. Box 1892, Houston, TX 77251-1892
Klaus Holliger
Inst. of Geophys. CH-8093 Zurich, Switzerland
A new general hybrid technique, HARVEST (hybrid adaptive regime viscoelastic simulation technique), to solve the 2-D acoustic/viscoelastic equations for problems which encompass different wave propagation regimes, such as the relatively smooth water column and the highly heterogeneous seafloor in deep ocean seafloor scattering experiments, is presented. A Gaussian beam method is used to propagate the source field through a vertically heterogeneous water column to the scattering region near the seafloor. This extrapolated source field is inserted into a viscoelastic finite-difference method used to compute the complex acoustic/anelastic interaction of the wave field with the rough seafloor. The backscattered field is extrapolated to a receiver array distant from the scattering locale by means of the Kirchhoff integral. HARVEST is employed to simulate ocean acoustic reverberation data collected during the 1993 ARSRP (Acoustic Reverberation Special Research Program) Acoustics Cruise. HARVEST is found to successfully reproduce ocean acoustic data within the confidence limits imposed by knowledge of seafloor morphology and material properties. The nature of scattering targets is interpreted from acoustics data in terms of synthetic HARVEST simulated data. In particular, rough basement that barely protrudes the sediment cover may cause strong returns in the backscattered field.