Wave-equation-based Residual Moveout Inversion In the Subsurface Angle Domain For Sub Salt Velocity Model Building

Wave-equation (WE)-based residual moveout (RMO) inversion for migration velocity analysis aims to update model parameters related to the seismic wave velocity using WE migration common image gathers (WEMCIGs) as input. Here we explain how to use RMO, picked on subsurface angle gathers (a type of WEMCIG), for velocity model building through angle domain sensitivity kernels. We show how to compute finite bandwidth sensitivity kernels that relate the depth shift of the image to a local change of the velocity. These sensitivity kernels replace ray-traced Fre´chet coefficients in conventional reflection tomography. In this way we can formulate the inverse problem that finds the velocity model by minimizing RMO without having to rely on ray-tracing, while keeping a lot of the inversion functionality of the conventional model building implementation in place. We show how to use RMO inversion in the subsurface angle domain for sub salt model building using the Sigsbee2A synthetic 2D model. We find that in such a complex setting combining subsurface angle gathers with angle-domain sensitivity kernels allows for WE-based RMO inversion in areas where the ray-based methods break down.