Motivation of the paper in big frame is to determine some anisotropic properties under surface of the earth like tunnels, empty areas or dielectric pipelines. It is well known, that for some frequencies of the electromagnetic waves the earth is pretty transparent and field penetrates into the ground. Reflected outgoing wave must contain information about the structure underground surface. This article concerns to the investigation of the complete reflected field from the ground in order to detect anisotropy under surface, particularly (farther), the tunnel, located inside ground using the incident electromagnetic waves. The goal of the work is to determine whether the tunnel is inside the ground or not. The Method of Auxiliary Sources (MAS) is used to solve the stated problem. As a sensitive method, the resonant properties of the tunnel are studied. The investigation is based on the fact that reflected field frequency characteristic measured in the point above the ground contains information (approximately the size and orientation) about the tunnel inside the ground.