An improved inverse scattering imaging condition based on ray-Kirchhoff approximation

Abstract

Reverse time migration (RTM) has superiority over other imaging algorithms in handling steeply dipping structures and other complicated geological models by directly solving the full two-way wave equation. Conventional RTM algorithms aim at generating structural images that indicate the geologic interfaces. Amplitude-preserving and low wavenumber artifacts removal are two important issues that should be addressed for improving imaging quality using RTM. The RTM inverse-scattering imaging condition has been introduced to account for these two key points. The original RTM inverse-scattering imaging condition adopts the ray-Born approximation. The Born approximation assume model perturbations have shot characteristic wavelengths and adopt a volume integral representation to establish the linear relationship between model and data perturbations. In this paper, we extend the concept of RTM inverse-scattering imaging condition by introducing Kirchhoff approximation for linearized forwarding modeling. Since the Kirchhoff approximation requires that model perturbations exist across smooth surfaces, the proposed imaging condition is more suitable for imaging locally planar seismic reflectors instead of superposition of point scatters which implied in Born approximation. Meanwhile, the advanced features of original RTM inverse-scattering imaging condition, i.e., amplitude-preserving and low wavenumber noise removal are well maintained. We verify the effectiveness of the present RTM imaging condition with both synthetic and field data.