Measurement of the Elastic Properties of the Ocean Bottom by Inversion of Reflection Amplitude Data

Abstract

A method is described for estimating the elastic properties of ocean bottom materials by inversion of acoustic reflection amplitude data. The amplitude of the reflected signal depends on the angle of incidence and the contrasts in the elastic properties of the media across the sea floor, and we assume that this relationship can be described by the plane wave reflection coefficient. Ocean bottom reflections are analyzed using a nonlinear parametric inversion to infer the density and the compressional and shear wave speeds in the surficial layer of sea floor material. Results are presented for inversion of data from experiments in sedimented and basaltic regions off the west coast of Canada. The data were obtained using either a fixed receiver and a moving source, or a towed source and reciever. For the latter case the reflections were first processed as common midpoint data. The estimates of the elastic properties are in good agreement with ground truth data from sediment cores and with seismic refraction profiles obtained in the same region.