Prestack depth imaging in complex structures using VTI fast marching traveltimes

Abstract

The presence of sedimentary layers in the Earth’s subsurface results in seismic anisotropy, which makes wave velocity dependent on the propagation angle. This phenomenon causes complexities and errors both kinematically and dynamically in seismic imaging. Among these errors are the mispositioning of migrated events and failure to retain energy during dip-moveout. A fundamental and challenging issue in seismic imaging is the computation of seismic wave traveltime from the source to the receiver via the reflection point. A powerful method for determining traveltime is the application of finite difference to solve the eikonal equation. In this study, we employ a fast marching eikonal solver in the isotropic and vertical transverse isotropy (VTI) concepts. We also test the results by using the Kirchhoff depth migration algorithm. Instead of using a linear eikonal equation, which is commonly used in the industry, we consider a nonlinear approximation because it is more realistic and accurate than the former. The Marmousi synthetic data and a real dataset are used for testing purposes. The comparison of isotropic and VTI traveltimes demonstrates a considerable lateral difference among wavefronts. The results of Kirchhoff imaging show that the VTI algorithm generates images with perfect positioning and higher resolution than the isotropic one, specifically in deep areas. Finally, we conclude that our anisotropic approach is stable, fast, and generates high-quality images with accurate details in deep structures.