SENSITIVITY OF REFLECTED AND TRANSMITTED SEISMIC DATA

Seismic data have been reported to carry information on both small scale and large scale medium variations, but not for intermediate size objects. This is a paradox compared to many other experiments performed with probes of wave nature, where objects of size of the smallest wavelength or larger can be resolved. The sensitivity of reflected and transmitted seismic data to medium perturbations of varying sizes is investigated. The differences between data generated in a reference model and data generated in a perturbed model are measured. Both L1 and L2 type objective functions are used. The kernels of the objective functions consist of either stress or particle-velocity field components. Several experimental configurations and the sensitivity to various ways of performing the medium perturbations are analyzed. For all perturbation types that change the impedances, we find a resonant behavior in the objective functions for perturbations of size of the typical wavelength of the source. For the experiments where impedances are kept fixed, we do not find this resonance, but there is a significant contribution to the objective function for all perturbation sizes larger then the shortest wavelength. That is, seismic data are sensitive to objects of size of the smallest wavelength or larger.