Patent ID: 8902700

Claim:
A method of acquiring seismic data in a borehole seismic survey comprising lowering into the borehole a cable comprising an outer sheath enclosing a plurality of pressure sensors arranged in a succession of groups spaced along the cable with each group comprising at least three pressure sensors spaced from each other in directions transverse to the cable; transmitting seismic signals from a seismic source outside the borehole and spaced from it so that seismic signals travel through subterranean formation between the source and the borehole before reaching the borehole; using said plurality of pressure sensors of each group to measure pressures and also measure pressure gradients in two directions transverse to the longitudinal direction of the cable, the pressures and pressure gradients being of seismic signals from the seismic source converted at the boundary of the borehole into pressure waves.