The Influence of Time Shift Wavelet on the Migration Imaging Accuracy

The imaging problems of common shot data with prestack reverse time migration method are solved with the forward continuation of source wave field and the backward continuation of receiver wave field in depth direction at the same time. In order to obtain imaging value, the conventional method is that the two wave fields implement cross correlation at the same time and stack the cross correlation value at all the same time. This method is fit for the case where the seismic wavelet is a pulse or minimum phase. However, in generally speaking, the event picked from seismic record is the peak of seismic wavelet which has a short time shift relative to the wavelet initial time. It subsequently results in some imaging position errors in cross correlation method. In this paper, theoretical seismic record are simulated and migrated by wave equation finite element prestack reverse time migration method with cross correlation imaging conditions. The influence of the time shift wavelet both in seismic source wave field and receiver wave field on the imaging accuracy is discussed. Numerical experiments demonstrate that the influence of time shift wavelet on the position error is related to the relative delay length of the peak of wavelet in the two wave fields and the medium velocity around the reflection point. The results provide a theoretical reference for the selection of seismic wavelet, which is important to the application of the cross correlation imaging conditions in prestack reverse time migration method.