Travel-time tomographic imaging: multi-frequency diffraction evaluation of a medium with a high-contrast inclusion

This paper presents the results of a numerical and experimental parametric study for the interpretation of the multi-frequency P-wave travel-time tomographic inversion of high-contrast heterogeneous media. A wide range of wavelengths was selected to simulate diffraction propagation regimes where the straight-ray assumption has limited application. In the numerical study, parameters such as operating wavelengths, source–receiver directivity, and ray bending effects were considered to improve the quality of travel-time tomographic inversion by interpreting internal scales of material–wavelength interactions. In the experimental study, two cylindrical concrete specimens with high and low-density inclusions were tested and tomographic images were obtained using three different wavelengths. Numerical and experimental results indicate the importance of wavelengths and curved ray solutions in the inversion of high-quality tomographic images of media with high-contrast inclusions.