Robust Synthetic Aperture Imaging of Marine Controlled-Source Electromagnetic Data

The synthetic aperture (SA) method has recently found applications in the analysis of the low-frequency marine controlled-source electromagnetic (MCSEM) data. It has been shown that this method can enhance the response from an anomalous target. However, in a SA method, anomalous EM fields and the noise will be equally steered and focused, leading to amplifying the noise and introducing artifacts into the images. In addition, the current realizations of the SA method are very sensitive to the noise in the data and the parameters of the SA. In this article, we address these difficulties by introducing a robust SA (RSA) method. The RSA method consists of three steps, namely, robust smoothing of the background field, robust interpolation of EM fields from the real receiver positions to the virtual receiver positions, and estimating the SA weights with a robust optimization scheme. The synthetic model studies show that this method is stable to noise and has a relatively high spatial resolution. We have also applied this method to the towed streamer data collected in the Barents Sea. The generated pseudo-3-D images accurately reveal the locations of the salt domes and fault structures known from the seismic data.