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In this work, we present an application of full-waveform inversion to a set of regional lines acquired over 1995–1996 years in the northern part of the Kazakh sector of the Caspian Sea ( Usserbayev et al., 2011 ). The main challenges in this area include salt-dome tectonics, strong short-wavelength multiple reverberations caused by the ultra-shallow water environment and the presence of high-contrast and laterally variable mixed terrigenous-carbonate near-surface layer. These factors complicate the depth velocity model building, particularly in the shallow part of the subsurface. An additional challenge in this project was the mixed acquisition design, which combined ocean-bottom cable and towed streamer data along the same lines. Nonetheless, full-waveform inversion has proven successful in these settings, yielding a reliable near-surface velocity model that aligns with data from nearby wells. In this work, we discuss the processing workflow, highlighting the innovative techniques that contributed to the successful application of this approach