Double-difference constrained reflection tomography

Abstract

Summary The inverted velocity model obtained from the reflection tomography based on the ADCIGs has a certain fuzziness. The inverted velocity model’s stratigraphic interface is always not clear enough in areas with complex stratigraphic structure. In order to improve the accuracy and resolution of the inverted velocity model, a double-difference constraint condition is added on the basis of minimizing the absolute travel-time residual at the subsurface imaging points. This constraint makes the inverted velocity model local structure information more refined by minimizing the differential travel-time residual at adjacent imaging points, and makes the variation of velocity model information within a certain range more accurate. The method in this paper is based on angle domain common imaging gathers(ADCIGs), the tomography inversion equation is established by using the Langan ray tracing method and the conversion relation between the travel-time residual and the residual curvature of the ADCIGs. Then, by adding differential constraint and double-differential constraint conditions and using LSQR to solve the set of equations, the inverted velocity model can be obtained through multiple iterations, which provides a high-precision velocity field for the migration and improves the accuracy of seismic imaging.