Wavefield tomography using image - warping

The main objective of this thesis is to study new methods for estimating the macro velocity model, which controls the wave kinematics, in the context of reflection seismology. Migration velocity analysis evaluates the quality of the velocity model used for imaging seismic data by comparing images of the subsurface structures as a function of extension parameters, such as offset, reflection angle, or shot-index. The angle domain has proved to be a suitable domain for velocity analysis because of its robustness against the noise introduced by the migration operator and against the ambiguities due to complex wave propagation in the subsurface. Nonetheless, angle gathers require an extra computational effort especially in full azimuth 3D scenarios. On the other hand, most migration algorithms naturally process the reflection data and output images in the shot-domain, which is usually regarded as a poor option for velocity analysis. The ability to extract reliable information about the velocity model from single-experiment images has value not only for the construction of macro velocity models for imaging but also for the regularization of high-resolution data-fitting techniques in a way that is compliant with the physics of wave propagation. In this thesis, I investigate how to make shot-domain velocity analysis algorithms more robust by exploiting the coherency of the structural features in the migrated domain and using the concept of image-warping. I link the difference between two migrated images with the concept of image-warping and show that with image-warping, one can obtain an approximation of the image difference that is less sensitive to the distance between the shot points. I use the image-warping approximation of the standard image difference as the input of a linearized inversion scheme to reconstruct the velocity anomaly in the migration model. The linearized inversion is based on one-way migration algorithms and relies on a series of assumptions about the strength of the perturbation in the wavefields and in the model. In order to remove these assumptions, I use the insight gained about the relationship between