Dynamically focused beam migration in anisotropic media

Abstract

As an improved ray method, Gaussian beam migration overcome the imaging problems of caustics area and shadow area in Kirchhoff migration, and to avoid the time-consuming problem of wave equation migration. It gives not only ideal calculation efficiency, but also high imaging accuracy. However, the accuracy of the Gaussian beam migration is controlled by the initial beam width at the surface. In this paper, we extend Nowack (2011)’s method to anisotropic media and present an anisotropic dynamically focused beam migration by modifying the propagator of Gaussian beam. We use anisotropic kinematic and dynamic ray tracing to obtain travel time, trajectory and dynamic information. Then we use dynamically focused beam of anisotropic media to calculate the Green’s function and the Claerbout’s imaging condition to obtain images. This strategy enables us to enhance the amplitude and improve the imaging quality in the middle and deep layer without reducing the imaging quality in the shallow layer, which will help to overcome the limitation of the initial beam width in Gaussian beam migration. The results of VTI Shengli complex structure model show the accuracy and validity of the research method in this paper which can solve the amplitude preserving imaging problem of deep complex anisotropic subsurface structure.