Local Angle Domain Kirchhoff Prestack Depth Migration in TI Media.pdfVIP

Local Angle Domain Kirchhoff Prestack Depth Migration in TI Media Pengfei Duan* and Jiubing Cheng School of Ocean and Earth Science, State Key Laboratory of Marine Geology, Tongji University Summary To support velocity analysis and amplitude variation with incident angle analysis in transversely isotropic media, we present a ray-based local angle domain prestack depth migration algorithm to generate common-image gathers in scattering and illumination angle domain. An efficient kinematic ray tracing system is used to construct numerical tables of traveltime, geometrical spreading factor and take- off angle of various raypath between the image-point and source or receiver on the surface. Weighted superposition of all impulse responses according to the local angular attributes of the raypath generates scattering and illumination angle domain migrated images. Synthetic examples on the SEG/HESS VTI model and the overthrut TTI model demonstrate the validity of this algorithm Introduction In traditional prestack seismic processing, common-image gathers (CIGs) provided by common-offset or common- shot migration is commonly used for migration-based velocity analysis or amplitude variation with offset (AVO) analysis. But it has been proven that offset- and shot- domain CIGs contain unexpected kinematic and dynamic artifacts in complex areas with strong lateral velocity variations (Nolan and Symes, 1996; Xu et al., 2001). In order to overcome these artifacts, some authors (e.g., de Hoop et al., 1994; Xu et al.,1998; Brandsberg-Dahl et al.,1999) suggested constructing the CIGs in the common scattering angle domain based on ray-theory. Angle- domain imaging algorithms in the frame of wave-equation migration have also been extensively studied (e.g., Prucha et al.,1999; Xie and Wu, 2002; Sava and Fomel, 2003). Compared with wave-equation migration, Kirchhoff-type migration has the advantage of efficiency and flexibility. The industry h