Low‐frequency geoacoustic modeling in shallow water sediment environments.

Abstract

The goal in geoacoustic modeling is to develop realistic geophysical models of the ocean bottom that can be used in numerical calculations of the acoustic field in the ocean. The ocean bottom is assumed to be a layered structure of different types of sediment material that have been deposited over geological times. However, in shallow water the bottom is generally much more complex. The sediment material is variable on different spatial scales horizontally and is inhomogeneous in depth below the sea floor. Despite this complexity in realistic bottom environments, there has been considerable success using the simplified approach of a layered, range‐independent geology in low‐frequency (20–500 Hz) applications with inversion techniques that provide estimates of geoacoustic model parameters and their uncertainties. This paper reviews some of the most effective inversion techniques and compares their performance in estimating realistic and effective geoacoustic profiles in applications with data from the recent Shallow Water ‘06 experiments on the New Jersey continental shelf. Conditions are discussed that limit the performance of present day inversion techniques. These include rough interfaces on and below the sea floor, consolidated material that supports shear wave propagation, and range variation of sub‐bottom structure.