Abstract：In face of the problem of building prestack depth migration velocity model, the paper deeply studied two methods for inversion of operator and velocity model in CFP half migration domain,that is synchronous inversion and asynchronous inversion.The former adjusts DTS response to align gather's event and to position zero timing line by changing velocity model.Each change of velocity model is followed by calculating focusing operator,CFP gather and DTS response and then using DTS response to calculate corrections of velocity model.The method mainly uses isochronal principle,in which the modification of velocity model and the picking up DTS gather are closely related together.The method is straightforward and reliable.The main efforts are in picking up DTS response.The asynchronous inversion of operator and velocity model is iterative calculation of correct focusing operator first according to the principle of error symmetry,then inversion of velocity model is proceeded on the basis of operator separately,that bears no relation to picking up DTS response.The method got velocity model indirectly but greatly reduced the work effort of picking up. In comparison with velocity analyzing method in an ordinary migration domain,the analysis in CFP half migration domain can be carried out at single geometric point on reflection interface and no windowed re migration is needed,which greatly reduced computational effort;furthermore,there is no assumption of short offset or small dip that often exists in ordinary migration methods,that is suitable for analysis of migration velocity in complicated subsurface medium.The test results with synthetic and real data show that the method is feasible.
