Locating near-surface scatterers by seismic interferometry of scattered surface waves: Investigating the effect of an offline cavity

A recently developed method based on active-source seismic interferometry and inversion is used to find the location of an offline (out of plane) near-surface scatterer. In the method a 2D geometry has been considered and the interferometric estimates of the scattered surface waves have been obtained for different locations of virtual sources. The interferometric traveltimes of these scattered surface waves were used in inversion to find the location of the scatterer. It has been shown that only one source at the surface is sufficient to successfully obtain the location of an inline scatterer. In this study an offline scatterer, a cavity, is considered to understand the effects of a 3D medium in estimating the location of the scatterer using the method. As expected, the location of the offline scatterer is estimated with some error when 2D geometry and related formulas are considered. In case of inline shot profiles, one should consider the possibility of an offline scatterer and be aware that the estimations of location can be effected by the existence of an offline catterer and cause misinterpretations.