Prestack depth migration using straight ray technique(SRT)

Abstract

Kirchhoff prestack depth migration requires an elaborate book-keeping effort and a massive IO process to construct Kirchhoff hyperbolas. In order to avoid the complexity of the programming code and the massive IO process, we propose a straight ray technique (SRT) for traveltimi calculations in Kirchhoff migration. Since all the rays are straight in. polar coordinates for the 2D velocity model,or in sphericalc oordinatesf or the 3D velocity model, traveltimesc an 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 clrcumvent the substantial IO process required for reading traveltimes on a disk and save computationals torage.N umerical examplesd emonstrateth at SRT computest raveltimesi ntermediate 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 misration for the SECiEAGE salr dome data.