First-arrival Slope Tomography of OBS Data

First-arrival slope tomography of OBS data is implemented. Because of sparse distribution of OBSs, it's difficult to pick the slopes of the seismic events at the receiver points in the common shot gathers We propose a technique for picking the slopes of the seismic events at the shot points and receiver points in the common receiver gathers, based on the phase-shift wave field extrapolation with an undulating datum and the reciprocity principle. Then we propose the first-arrival slope tomography of OBS data, which used combined the first-arrival travel-times and slopes to estimate the underground velocity. To test the performance of this method, we built a velocity model according to the geological structures of the South Yellow Sea, China and synthesized the OBS data with the model, simulating the real OBS observations in the South Yellow Sea We applied the method to build the velocity model from the synthetic OBS data. The results show that this method can improve the resolution of the velocity model built.