Computation of Kinematic Attributes for Pre-stack Time Migration

In many areas time imaging still represents the majority of seismic imaging activity in the industry. In this context pre-stack time migration remains a central process. We propose a new approach for estimating various kinematic attributes associated with pre-stack time migrated results. Our approach is based on a kinematic demigration of locally coherent events characterized by their position and dip in common offset time migrated images. The reflection angle, the instantaneous velocity or the geological dip can be estimated with the assumption that time imaging exactly positions laterally the events. In addition, the stretch factor and the "kinematic invariants" (the demigrated facet in the unmigrated domain!) can be recovered accurately independently of the positioning accuracy of time imaging. As opposed to many conventional approaches, the estimation is directly based on the travel time curves used in pre-stack time migration with no assumption regarding the structural dips or the lateral variations of the velocity model. The attributes may be used at various steps of the processing sequence: stretch factor to design de-stretching operators, reflection angle to design partial angle stacks for AVO/AVA studies and kinematic invariants to perform reflection tomography.