Abstract：Pre-stack depth migration technique can be realized either in shotpoint-receiver domain or in CMP-offset domain.The predecessors popularized split-step extrapolation operator into DSR pre-stack migration based on phase-shift in CMP-offset domain.The simple and high-efficient split-step DSR pre-stack depth migration has been resulted from correction for errors produced by phase-shift extrapolation in constant velocity using time-shift quality only once within each step length of downward continued wave field,but this method has a poor precision.Based on non-stationary phase-shift formula for wave field extrapolation and through introducing reference velocity,the paper deduced a new high-order screen approximate formula conducted wave field continuation in CMP-offset domain,using Taylor's series extension for two square roots in DSR and suitable mathematical process.The formula can directly conducted continuation to pre-stack wave field in CMP-offset in high-efficiency.Through increasing order of screen,the precision of pre-stack depth migration in a condition of strong lateral changes in velocity has been improved.The method is extension of pre-stack depth migration by split-step DSR.The test results from theoretical model and real data showed that the method is effective and practical.
