Abstract: Depth of a top (24) and bottom (28) of an under water mud layer (26) are measured as a function of position from acoustical scattering measurement. The measurement involves transmitting sound from a transmitter (12) in a body of water (22) above the mud layer (26), using a higher and lower frequency range, above 100 kHz and below 20 kHz respectively. A higher frequency signal due to scattering of the sound in the higher frequency range from scatter positions along a selected horizontal direction is detected as a function of time from said transmitting, and a first depth, of a top surface (24) of the under water mud layer (26), is computed using this signal. A plurality of received lower frequency signals due to scattering of the sound in the lower frequency range is detected at different height in the body of water (22).

Abstract: A new approach is described based on reciprocity for estimating acquisition-related effects, which has several advantages over conventional surface-consistent processing techniques: (i) It can be applied to complete recordings, hence does not require the isolation of primary reflections in the data, (ii) no assumptions are imposed on the subsurface, and (iii) it is applicable to multi-component data. The application of reciprocity requires symmetric data acquisition, i.e. identical source and receiver patterns, identical locations, and the source orientations have to be identical to the receiver components. Besides reciprocity, additional constraints are required to determine the lateral source and receiver amplitude variations fully. Criteria based on minimizing total energy differences between adjacent common source and common receiver gathers, and in common offset panels of the medium response are applied.

Abstract: The invention concerns a method for retrieving local near-surface material information including the steps of:—providing a group of receivers comprising at least one buried receiver and at least one surface receiver positioned either at or very near the Earth surface;—recording a seismic wavefield;—estimating a propagator from said recorded seismic wavefield;—inverting said propagator; and—retrieving said near-surface material information.

Abstract: The invention concerns a method for retrieving local near-surface material information including the steps of:—providing a group of receivers comprising at least one buried receiver and at least one surface receiver positioned either at or very near the Earth surface;—recording a seismic wavefield;—estimating a propagator from said recorded seismic wavefield;—inverting said propagator; and—retrieving said near-surface material information.