Wave Equation Pre-stack Depth Migration And Migration Velocity Error Analysis

Wave equation pre-stack depth migration is an ideal seismic data imaging technique for the area where there occur very complicated geologies structure and sever lateral velocity variation. The PSDM results allowed for high Precise geologic and structure interpretation in complex regions. The key Point of depth migration is the wave field extrapolation operator. There are several common operators; they are PS, SSF and FFD. Numerical examples indicate that each operator has its advantage and limitation,we must consider imaging accuracy and time consumption according to the feature of the media before migration is performed. Nowadays,one-way wave equation is used for zero- offset seismic numerical simulation in most times, however, they are scarcely used in the field of nonzero-offset seismic numerical simulation for the reason of incomplete theory and leaking in efficient algorithm. Taking advantages of one- way wave equation methods, the Paper realize one-way wave-field extrapolation operators, zero-offset seismic modeling, nonzero-offset seismic modeling with irregular surface, Post-stack and Pre-stack migration with SSF:First, In order to provide input for Pre-stack migration, we generated common-short record based on Huygens's principle. Compared with other modeling strategy, our method is more efficient,the types of wave are more complete and clear, and the signal- to-noise ratio is higher. It enables us to choose wave field extrapolation operator freely, and the method is available when the recording geometry is complicated such as rugged earth surface.Second, the Processing of relief surface is a key factor for imaging in complex area. During the nearest ten years, many people have done much study in this area, and there are methods such as wave-equation datum correction, zero velocity method, wave field upward continuation etc…A pre-stack depth migration method from irregular surface directly is programmed. The computing result shows that it's an effective approach handling complex surface.Third, the acoustic wave equation depicts the physical principle of the wave phenomenon. This thesis bases on the acoustic wave equation, discusses the theory of foundation and methods of migration velocity error analysis based on the acoustic wave equation,and author takes some numerical simulation tests to display the bad effect wave field characteristic caused by velocity error.