Forward and Inverse Analysis of Love Wave Scattering by Interface Cavities

Love waves have great potential in geological inspection and ultrasonic nondestructive testing for near-surface underground characteristics. A thorough and effective utilization of the Love wave requires a better understanding of its scattering phenomenon. The paper studies the problem of Love wave scattering by cavity-like flaws on the interface between the upper layer and the lower half-plane. For the forward analysis, we suggest a modified boundary element method (BEM) incorporating the far-field displacement patterns, which can effectively eliminate fictitious reflections introduced by model truncation. For inverse analysis, we propose a quantitative reconstruction procedure for the flaw shape using reflection coefficients of the first-order Love wave. By theoretical deduction, it can be proved that the cavity's geometric shape is approximately expressed as an inverse spatial Fourier transform of far-field reflection coefficients in the wavenumber domain. Numerical examples are given by substituting the reflection coefficients obtained from the forward analysis into the inversion algorithm, and high consistency is shown between the reconstructed flaw images and the geometric characteristics of the actual flaws.