Prestack depth migration using straight ray technique (SRT)

Abstract

Kirchhoff prestack depth migration requires an elaborate book-keeping effort and a massive 10 process to construct Kirchhoff hyperbolas. In order to avoid the complexity of the programming code and the massive 10 process, we propose a straight ray technique (SRT) for traveltime calculations in Kirchhoff migration. Since all the rays are straight in polar coordinates for the 2D velocity model,or in spherical coordinates for the 3D velocity model, traveltimes can be simply computed along a straight ray for a given source-receiver configuration, without suffering from shadow zones and caustics, and used directly for building Kirchhoff hyperbolas. In this way, we circumvent the substantial 10 process required for reading traveltimes on a disk and save computational storage. Numerical examples demonstrate that SRT computes traveltimes intermediate between first-arrival traveltimes and the most energetic arrival traveltimes, resulting in better images than the first arrival traveltimes for the 2D IFP Marmousi data. With the implementation of SRT for 2D Kirchhoff migration, we successfully extend our SRT to 3D Kirchhoff migration for the SEG/EAGE salt dome data.