Source Signature Estimation - Attenuation of the Seafloor Reflection Error in Shallow Water

Ziolkowski et al. (1982) presented a method for computing the monopole pressure field - the notional source signature - of each airgun or airgun cluster in an array from a set of near-field hydrophone measurements. The notional source signatures are then used to compute the far-field signature of the source array. In areas where the seafloor is hard or in shallow water, the seafloor reflection can cause reverberations of significant amplitude in the near-field measurements. Left uncorrected, the seafloor reflections may lead to a significant error in the far-field signature. Kragh et al. (2000) used an adaptive beamformer to remove these reflections. However, in water depths shallower than about 40 m, an alternative method is required. In this paper, we present an extension to the notional source method of Ziolkowski et al. (1982) that includes the water column reverberations measured by the near-field hydrophones in very shallow water.