Enhancing Subsurface Diffractions Using Demigration Method

Abstract

Diffractions can correctly identify the geological discontinuities as they are physically reliable carriers of high-resolution structural information. However, weak diffraction waves are often masked by specular reflection waves. Therefore, we propose the methods for enhancing diffraction waves using the Kirchhoff demigration method with a dip-based weight function. As the natural asymptotic inverse of the Kirchhoff migration, the Kirchhoff demigration can be used to model the wavefield. In this study, we demonstrate the different behaviors of diffractions and specular reflections during demigration, and how this can be leveraged to suppress reflections and enhance diffractions. During demigration, reflection waves mainly originate from rays in the Fresnel zone around the stationary point. By designing a dip-based filter, these rays are suppressed to destroy reflection waves. In this way, the diffraction-only waves can be obtained even in the amplitude sharp change case. The overthrust and field data applications show the potential of this method in separating diffractions and highlighting geological discontinuities.