Sound velocity inversion in layered media with band-limited and noise-corrupted data.

Abstract

With reflection data measured from two different incident angles, it is possible to make them "nearly the same" by stretching or contracting the time axis of one of them. In this way, a correspondence is built up between the two travel times, which can be used to calculate the one-dimensional sound velocity profile of the medium. For the special case that the impulse response of the medium consists of sparse spikes, a spectral fitting procedure is developed which deconvolves the received signal, and gives the exact positions of the spikes. The stepwise sound velocity profile can then be calculated from these positions. In experimental measurements the plane wave assumption made in the analysis is not true, but this can be accommodated with some modifications of the calculation. Results of both computer simulation and of measurements are presented, indicating the validity of these processings.