Abstract: To compare the pre-stack migration in the time domain (PSTM), the pre-stack migration in the depth domain (PSDM) can adapt to the seismic data which has the high dip angle and the large variation of the velocity in the horizon. Based on the imaging principle of Kirchhoff pre-stack depth migration method, we established the initial velocity model at first; then added the target geological body-Salt Dome to the initial velocity model,and further optimized it;under the constraints of the horizon of the salt dome, we computed the difference of two travel times through a lot of iterations so as to update the initial velocity model. By the updated initial velocity model, the Kirchhoff integral method is used to migrate the seismic data. The job can be finished if the corrected reflection phase of the common imaging point gather is at the same level;if not, the horizon of the salt dome has to be modified again and again. We can modify the horizon by use of the well logs and the geological knowledge or consult with the geological experts. Taking this new modeling approach, the latter image has higher S/N and resolution compared to the results of the PSTM imaging methods under the constraints of the horizon of the salt dome. The specific performance is the clear breakpoint, outstanding wave group characteristics; especially, the outline of the salt dome has very clear boundaries, and the bottom of the salt dome image is also much more improved than that of the image of the PSTM.

Key words: pre-stack migration in the time domain, pre-stack migration in the depth domain, geological model