High resolution three dimensional electromagnetic survey method

A method for electromagnetic surveying below the bottom of a body of water includes deploying a plurality of nodal recording devices 24 in a selected pattern on the water bottom. An electromagnetic transmitter 16A, 16B is towed in the water. At least one electromagnetic sensor streamer 20 is concurrently towed in the water. The electromagnetic transmitter is actuated at selected times and signals detected by sensors in the nodal recording devices and in the at least one streamer are recorded. The present invention combines the relatively high depth resolution of nodal EM recording systems with the spatial resolution of towed EM streamer systems. It identifies both shallow and deep targets while increasing overall acquisition efficiency as the EM transmitter only needs to be moved once through the survey area for both streamer and receiver node data acquisition. Signals detected by the sensor streamer in response to the transmitter may be corrected for magnetotelluric effects using magnetotelluric signals detected by the nodal recording devices.