Abstract:
This thesis introduces an algorithm for inverting for the geoacoustic
properties of the seafloor in shallow water. The input data required by the
algorithm are estimates of the amplitudes of the normal modes excited by a
low-frequency pure-tone sound source, and estimates of the water column
sound speed profiles at the source and receiver positions. The algorithm
makes use of perturbation results, and computes the small correction to an
estimated background profile that is necessary to reproduce the measured
mode amplitudes. Range-dependent waveguide properties can be inverted
for so long as they vary slowly enough in range that the adiabatic
approximation is valid. The thesis also presents an estimator which can be
used to obtain the input data for the inversion algorithm from pressure
measurements made on a vertical line array (VLA). The estimator is an
Extended Kalman Filter (EKF), which treats the mode amplitudes and
eigenvalues as state variables. Numerous synthetic and real-data examples
of both the inversion algorithm and the EKF estimator are provided. The
inversion algorithm is similar to eigenvalue perturbation methods, and the
thesis also presents a combination mode amplitude/eigenvalue inversion
algorithm, which combines the advantages of the two techniques.
