Ray methods for inverse problems of elastic wave scattering
Abstract
Inverse scattering methods based on time domain data are proposed, which are particularly suitable for the mapping of crack like flaws in homogeneous media. The methods require input data that can be either directly measured or computed from measured data. The first method maps a point on the scatterer by a process of triangulation with the source and receiver as given vertices of the triangle. The inverse mapping is global in the sense that no a priori knowledge about the location of the scatterer is necessary. The second method maps the scatterer by determining the envelope of a set of planes. For the case of cracks, the envelope maps an approximation to the crack edge. Also it is based on approximations valid only in the neighborhood of the edge, thus it is a local inverse mapping. The starting point for the triangulation method is Fermat's Principle, which states that first arriving signals describe geodesic curves.
 Publication:

Ph.D. Thesis
 Pub Date:
 1981
 Bibcode:
 1981PhDT........29N
 Keywords:

 Cracks;
 Elastic Scattering;
 Inverse Scattering;
 Mapping;
 Wave Scattering;
 Fermat Principle;
 Geodesic Lines;
 Geometrical Optics;
 Time Lag;
 Triangulation;
 Communications and Radar