Abstract: A geophysical data acquisition system includes at least one geophysical sensor. The at least one geophysical sensor has associated therewith a signal generator configured to generate a signal corresponding to a type of the at least one geophysical sensor. The system includes at least one signal acquisition unit having a plurality of input channels. The at least one geophysical sensor is in signal communication with one of the plurality of input channels. The plurality of input channels each includes a detector for receiving and identifying the signal generated by the signal generator. The at least one signal acquisition unit includes amplification, filtering and digitizing circuits automatically configurable in response to the type of sensor identified by the detected signal.

Abstract: A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface involves measuring magnetic field gradient in at least two orthogonal directions in response to the induced electromagnetic field and determining an electric field response in a direction normal to the magnetic field gradient measurements. A method for determining a component of electric field response of the Earth's subsurface to a time varying electromagnetic field induced in the Earth's subsurface involves measuring electric field response along a substantially closed pattern on at least one of the Earth's surface and the bottom of a body of water and determining an electric field response in a direction normal to the measured electric field response using electric field response measurements made at opposed positions along the closed pattern.

Abstract: A method of testing the electric field recording of a marine electromagnetic sensor cable including electrodes is provided. The method includes causing time varying current to flow between at least one pair of current electrodes disposed along the marine electromagnetic sensor cable. The flow of current generates a voltage in a body of water, thereby causing a secondary field impressed on a pair of sensor electrodes disposed along the marine electromagnetic sensor cable. A potential difference between the pair of sensor electrodes is measured. Accuracy of the electric field recording is inferred from the measured potential difference.

Abstract: A geophysical data acquisition system includes at least one geophysical sensor. The at least one geophysical sensor has associated therewith a signal generator configured to generate a signal corresponding to a type of the at least one geophysical sensor. The system includes at least one signal acquisition unit having a plurality of input channels. The at least one geophysical sensor is in signal communication with one of the plurality of input channels. The plurality of input channels each includes a detector for receiving and identifying the signal generated by the signal generator. The at least one signal acquisition unit includes amplification, filtering and digitizing circuits automatically configurable in response to the type of sensor identified by the detected signal.

Abstract: A method of testing the electric field recording of a marine electromagnetic sensor cable including electrodes is provided. The method includes causing time varying current to flow between at least one pair of current electrodes disposed along the marine electromagnetic sensor cable. The flow of current generates a voltage in a body of water, thereby causing a secondary field impressed on a pair of sensor electrodes disposed along the marine electromagnetic sensor cable. A potential difference between the pair of sensor electrodes is measured.

Abstract: A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface involves measuring magnetic field gradient in at least two orthogonal directions in response to the induced electromagnetic field and determining an electric field response in a direction normal to the magnetic field gradient measurements. A method for determining a component of electric field response of the Earth's subsurface to a time varying electromagnetic field induced in the Earth's subsurface involves measuring electric field response along a substantially closed pattern on at least one of the Earth's surface and the bottom of a body of water and determining an electric field response in a direction normal to the measured electric field response using electric field response measurements made at opposed positions along the closed pattern.

Abstract: A method for determining orientation of an electromagnetic survey sensor includes deploying the sensor at a selected position on the bottom of a body of water. An electromagnetic field is generated at a selected position in the body of water. A portion of the electromagnetic field is detected along at least two orthogonal directions at the sensor. A portion of the detected electromagnetic field is selected as having traveled only in a vertical plane which includes both source position and sensor position. The polarization direction of the selected portion of the electromagnetic field is determined from the selected portion. The determined polarization direction is used to determine the sensor orientation.

Abstract: A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface involves measuring magnetic field gradient in at least two orthogonal directions in response to the induced electromagnetic field and determining an electric field response in a direction normal to the magnetic field gradient measurements.

Abstract: A marine electromagnetic acquisition apparatus includes a sensor module having at least one sensor associated therewith. A sensor arm assembly is coupled to the sensor module. The sensor arm assembly has at least one sensor arm and at least one sensor disposed along the at least one sensor arm. An actuator is coupled to the sensor arm assembly for moving the sensor arm assembly between a folded position and an unfolded position.

Abstract: A method of testing the electric field recording of a marine electromagnetic sensor cable including electrodes is provided. The method includes causing current to flow between a pair of first electrodes disposed along the marine electromagnetic sensor cable. The flow of current generates a voltage that is impressed on a pair of second electrodes disposed along the marine electromagnetic sensor cable. A potential difference between the pair of second electrodes is measured. Accuracy of the electric field recording is inferred from the measured potential difference.

Abstract: A method for determining a component of electric field response of the Earth's subsurface to a time-varying electromagnetic field induced in the Earth's subsurface is provided. The method includes measuring electric field response along a nonlinear pattern on at least one of the Earth's surface and the bottom of a body of water. The method includes measuring magnetic field response in three directions along the nonlinear pattern on at least one of the Earth's surface and the bottom of the body of water. The method further includes determining an electric field response in a direction normal to the measured electric field response using the electric field response and magnetic field response measurements.

Abstract: A marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated with the module. The electrodes are arranged to measure electric field in a direction along the direction of the cable. The cable is arranged to form a closed pattern. Another marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated therewith. The electrodes are arranged to measure electric field in a direction along the direction of the cable. A plurality of spaced apart magnetic field sensors is associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

Abstract: A method of testing the electric field recording of a marine electromagnetic sensor cable including electrodes is provided. The method includes causing current to flow between a pair of first electrodes disposed along the marine electromagnetic sensor cable. The flow of current generates a voltage that is impressed on a pair of second electrodes disposed along the marine electromagnetic sensor cable. A potential difference between the pair of second electrodes is measured.

Abstract: A marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated therewith. The electrodes are arranged to measure electric field in a direction along the direction of the cable. A plurality of spaced apart magnetic field sensors is associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

Abstract: A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface involves measuring magnetic field gradient in at least two orthogonal directions in response to the induced electromagnetic field and determining an electric field response in a direction normal to the magnetic field gradient measurements. A method for determining a component of electric field response of the Earth's subsurface to a time varying electromagnetic field induced in the Earth's subsurface involves measuring electric field response along a substantially closed pattern on at least one of the Earth's surface and the bottom of a body of water and determining an electric field response in a direction normal to the measured electric field response using electric field response measurements made at opposed positions along the closed pattern.

Abstract: A method for measuring magnetotelluric response of the Earth includes measuring transient controlled source electromagnetic response of the subsurface below a body of water over a plurality of actuations of an electromagnetic transmitter. The transient response measurements are stacked. The stacked transient responses are subtracted from measurements of total electromagnetic Earth response over a time period including the plurality of transient response measurements to generate the magnetotelluric response.

Abstract: A marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated therewith. The electrodes are arranged to measure electric field in a direction along the direction of the cable. A plurality of spaced apart magnetic field sensors is associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

Abstract: A method for determining orientation of an electromagnetic survey sensor includes deploying the sensor at a selected position on the bottom of a body of water. An electromagnetic field is generated at a selected position in the body of water. A portion of the electromagnetic field is detected along at least two orthogonal directions at the sensor. A portion of the detected electromagnetic field is selected as having traveled only in a vertical plane which includes both source position and sensor position. The polarization direction of the selected portion of the electromagnetic field is determined from the selected portion. The determined polarization direction is used to determine the sensor orientation.

Abstract: A sensor cable system for measuring electromagnetic response of the Earth's subsurface includes a sensor cable deployable on the bottom of a body of water. The sensor cable has a plurality of electromagnetic sensing devices thereon at spaced apart locations. A system control unit is in signal communication with the sensing elements. The system control unit includes a transceiver for communicating signals to and from a corresponding sensor cable system. The system control unit includes a global positioning system signal receiver. The system control unit includes a processor configurable to receive signals detected by sensing elements in the corresponding sensor cable system. The processor is configurable to compute stacked signals from the sensing elements in the sensor cable and from sensing elements in the corresponding system. The processor is configurable to calculate a statistical measure of the stacked signals. The system control unit is disposed in a flotation device.

Abstract: A marine electromagnetic acquisition apparatus includes a sensor module having at least one sensor associated therewith. A sensor arm assembly is coupled to the sensor module. The sensor arm assembly has at least one sensor arm and at least one sensor disposed along the at least one sensor arm. An actuator is coupled to the sensor arm assembly for moving the sensor arm assembly between a folded position and an unfolded position.