Robust processing of noisy land-based controlled-source electromagnetic data

ABSTRACTWhereas robust processing techniques are routinely used for estimating high-quality magnetotelluric (MT) transfer functions, such techniques are not commonly applied for controlled-source electromagnetic (CSEM) processing, although CSEM and MT data suffer from similar noise. We implemented a new CSEM processing scheme that combines CSEM-specific preprocessing with statistically robust least-squares stacking to extract interpretable ground responses from very noisy onshore CSEM data. We applied the robust processing to signals from a new CSEM transmitter that was equipped with three grounded electrodes and allowed us to generate signals at multiple source polarizations with relatively little field effort. For this transmitter setup, we formulated a bivariate relation between the source currents injected through any two of the three source electrodes and the recorded electromagnetic field components. The resulting weighted least-squares system of equations from which we determined ground responses a...