The RAYINVR software, which is widely used in academia for 2-D velocity structure model from fourcomponent OBS (ocean bottom seismometer) data, is unable to invert for the converted S-wave automatically, resulting in the low-efficiency of modeling process. Using MATLAB’s genetic algorithm, the RAYINVR software is improved and able to automatically and synchronously invert for Poisson’s ratios of each layer with all subblocks for the S-wave velocity structure model, and thus can provide Young’s modulus, Poisson’s ratio and other important mechanical information for gas hydrate survey. This method is applied to process the OBS data collected at the Slipstream submarine slide, and a fine P- and S-wave velocity structure model is obtained, which is comparable to the logging data of nearby borehole U1326. Therefore, the validity of the auto-synchronous inversion method is verified for the S-wave velocity structure modeling. The optimal velocity model reveals two structural interfaces with large Poisson’s ratio contrast. One is BSR (bottom simulating reflector) at 230±10 mbsf (meter beneath sea floor), which represents the bottom boundary of the gas hydrate stability zone, and the other is the basal boundary of a shallow abnormal high-speed body (possibly a sand body enriched with high saturation gas hydrate) at 75?100 mbsf. The latter agrees roughly with the glide plane of Slipstream submarine slide, indicating that the hydrate is related to the formation of submarine landslide.