Long-Range CW and Time-Domain Simulations of Ocean Acoustic Scatter from Mid-Atlantic Ridge Corners

摘要

Long-range acoustic experiments done in the mid-Atlantic ridge region show strongbackscatter from many ocean bottom features. One type of feature characteristic of this region, and a possible contributor to this acoustic backscatter, takes the form of a seafloor ridge corner formed by two ridge faces intersecting at near-right angles. We have investigated through computer simulations the effects of an anelastic seafloor corner on the backscattered acoustic field. The acoustic source insonifying the seafloor corner was near the sea surface and approximately 4 km away in range. The ocean depth at the seafloor corner was also 4km. Simulations were made using cw computer models: the parabolic equation model, FEPE, for long-range propagation acoustics field to and from the vicinity of the seafloor corner; the finite-element marching-frame acoustic model, FFRAME, and the seismoacoustic finite-element model SAFE, to determine the backscattered field from the anelastic corner. Time-domain calculations were obtained from FFTs of the cw fields. Examples are presented that show large backscatter near the base of the ridge while relatively low backscatter near the ridge peak. This is attributed to the angle of the insonifying field and multiple scattering effects. Backscatter from a longer range (10-20 km), gently sloped, sedimented seafloor is also presented and discussed. (AN).