Geophysical data acquisition system

The invention includes a geographical sensor apparatus for use under water in the sea, including a plurality of seismic sensors ( 1 ) for sensing seismic waves associated with underground formations, and a plurality of EM-sensors constituted preferably by electrodes ( 4 ) for sensing electromagnetic waves associated with the underground formations. In a preferred receiver cable configuration embodiment of the invention, the geophysical sensor apparatus includes a seismic receiver cable with a linear array of a plurality of seismic sensors ( 1 ) and EM-sensors arranged inside a flexible outer skin ( 25 ), with the EM-sensors having electrodes on the outside of the outer skin. The cable is operated on the seafloor by a surface vessel, the vessel towing an electromagnetic transmitter antenna in addition to the seismic source.