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 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 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 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 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 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.

Abstract: A method for processing marine electromagnetic signal measurements includes acquiring magnetotelluric (MT) measurements from below a bottom of a body of water at a plurality of positions along the water bottom at substantially the same times at each position. Controlled source electromagnetic (CSEM) measurements are acquired from below the water bottom at substantially the same positions at substantially the same time at each position. The MT measurements and the CSEM measurements are jointly processed to obtain a model of conductivity distribution in the formations below the water bottom.

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 method for interpreting electromagnetic survey data includes acquiring electromagnetic survey data near a top of a portion of the Earth's subsurface. An initial model of the portion of the Earth's subsurface is generated. The model includes at least spatial distribution of formation resistivity within the portion. The initial model is applied to an artificial neural network trained to generate expected electromagnetic survey instrument response to the initial model. The acquired electromagnetic survey data are compared to an output of the artificial neural network. The initial model is adjusted, and the applying the model to the artificial neural network and the comparing are repeated until differences between the output of the network and the acquired survey data fall below a selected threshold.

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 method for interpreting transient electromagnetic survey data includes imparting an electromagnetic field in the Earth's subsurface by passing electric current through a transmitter antenna. The electric current includes switched direct current at a selected switching frequency. Voltages induced in a receiver corresponding to electromagnetic effects induced in the Earth's subsurface are detected. Frequency domain electromagnetic response of the Earth's subsurface is determined from the detected voltages and transient electromagnetic response of the Earth's subsurface is determined from the detected voltages.

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. A method for determining a component of electric field response to a time varying electromagnetic field induced in the Earth's subsurface, includes 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 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.