Study on the impulse response of seismic wave prestack reverse-time migration and its application

In order to better apply the seismic wave prestack reverse-time migration technology, we studied the impulse response of reverse-time migration. Starting from the impulse response of layered media model with offset, firstly, we discuss the genesis of low-frequency reverse-time noise of the conventional correlation reverse-time imaging conditions, analyze the advantages of the reverse-time migration conditions in up-going and down-going wavefield separation for suppressing low-frequency noise, and compare the impulse responses in the above two reverse-time migration conditions with smoothed migration velocity. Then, we analyze the influence of seismic wave numerical dispersion on the accuracy of the reverse-time migration impulse response under the conditions of different migration grid parameters and velocity distribution. The computational results show that the reverse-time background noise is mainly caused by the up-going reflection wavefield corresponding to the relative wave impedance difference interface during wavefield continuation. Velocity smooth can effectively reduce low-frequency background noise while decrease the accuracy of imaging. Seismic wave numerical dispersion is one of the important factors affecting the accuracy of reverse-time migration, and the selection of reserve-time migration parameters must be extremely obey the numerical dispersion relationship. Meanwhile, model testing proves the interchangeability of source and receiving point in reserve-time migration, which provides method guide for reserve-time migration. By optimizing reserve-time migration parameters, application on actual land data obtains good imaging result.