Scattered signal in time domain, which can be identified to have originated from mantle I and II, a void, or higher order scattering zone based on the travel-time of the received signal. The transmitted plane wave is indicated with gray. The wavefronts (1)–(6) correspond to the values given in Table 3. The gray and black arrows indicate the directions of the transmitter and the receiver, respectively. The wavefront (7) corresponds to a round trip inside the analog, starting from reflection number (6). High-order scattering zone includes multi-path and multiple scattering contributions.