Pre-stack migration and true-amplitude processing of DEKORP near-normal incidence and wide-angle reflection measurements

Abstract

An alternative to CMP-processing is presented which seems to be more appropriate to crustal seismics. It has been developed for wide-angle seismics but it can also be applied to near-normal incidence data. The essentials of this processing sequence are shot domain processing, retention of true amplitudes and pre-stack migration. True-amplitude processing of land data requires very careful editing. In addition, the ground coupling of individual sources and receivers must be taken into account by applying surface-consistent amplitude corrections. Subsequent pre-stack migration is very time-consuming. Although the isochron migration applied is based on kinematic principles, the amplitude distribution may be regarded qualitatively as an image of the reflectivity. The method can resolve steeply dipping reflectors and works with physically meaningful (dip-independent) migration velocities. The migration velocities are computed prior to migration by ray tracing using a macro velocity model. Robustness of the method can be increased by forming envelopes after single shot migration and stacking them to obtain a final image. When applied to DEKORP-data from near the German Continental Deep Drilling site (KTB), the Franconian Lineament fault zone (dipping at ∼55°) has been well imaged, in addition to many other reflectors throughout the crust. Furthermore, areas with high reflectivity can be distinguished from areas with low reflectivity due to the true-amplitude processing.