Imaging of the shallow subsurface using refracted and diffracted waves

A combined method including coherency inversion, tomographic imaging and homeomorphic imaging was used to locate inhomogeneities in the upper part of the subsurface. This method uses both refracted and diffracted waves. The travel times of refracted waves, which can be observed as first breaks on shot records, were used in coherency inversion to construct a low frequency velocity-depth model. Apparent intercept times representing initial data were taken from the refraction stacked section, which was created by applying linear moveout corrections to common shot records. Refraction tomography, using the simultaneous iterative reconstruction technique (SIRT), was carried out based on the model obtained from coherency inversion. Homeomorphic imaging is used to obtain continuous information on the shallow subsurface using diffraction travel time curves. A new parameter of this curve is the radius of curvature of the wavefront as used in the determination of local inhomogeneities in the geological section. This technique was also tested on a real data set.