Data preparation for prestack depth migration

Hugh D. Geiger

The goal of prestack depth migration is to reconstruct an image of the subsurface with the highest possible resolution. Given that seismic data is bandlimited, the ideal response from the complete sequence of data preprocessing and imaging is an image where each reflector is represented as zero-phase bandlimited singular functions with the peak positioned at the reflector and the peak amplitude proportional to the angle-dependant reflection coefficient. To achieve this goal, each step of the sequence needs to be understood and implemented correctly. This is a challenge even with the simplest constant-velocity synthetic data. Key considerations include: 1) preprocessing of the data to a zero phase wavelet, 2) accurate modelling of the source signature as a zero-phase wavelet, and 3) phase and amplitude stability of the extrapolators. 2-D synthetic models are used to show how uncorrected static shifts and non-zero-phase wavelets affect the resolution of the image.