Abstract: The following disclosure relates to a system for generating velocity models of salt and subsalt formations. The system provides accurate velocities for both salt and subsalt formations. In some embodiments, the disclosure relies on the combination of three elements: the “long offset” between seismic source and seismic receiver node, the use of multiple seismic signals at different geographic locations, and the refraction of the seismic wave off of the “basement” of the earth's crust. By combining the multiple seismic signals with the “fast basement,” which is accessible due to the long offset of sources and receiver nodes, it is now possible to determine a more accurate seismic propagation velocity for salt and subsalt formations by using FWI-based refraction tomography.

Abstract: Methods and apparatus are provided for reducing and/or substantially eliminating sensitivity mismatch of acoustic receivers used with acoustic sources to determine acoustic properties of geologic formations as a logging tool traverses the formations. Methods are directed to detecting waveform arrival times at receivers, determining places in a well where arrival times of waves are substantially the same at a plurality of receivers, and estimating effective receiver sensitivities and equalization factors using Stoneley wave amplitudes and windowed deconvolution of Stoneley waves. Methods are further directed to correcting wave amplitudes using estimated effective receiver sensitivities and equalization factors for receivers.