RTM Angle Gathers Using Analytic Wavefield

Angle gathers from RTM are important input for migration velocity model building and amplitude variation with angle analysis (AVA) in complex area, such as subsalt area. In this paper, we present a method to generate RTM angle gathers. This method decomposes both the source and receiver wavefield into their local angle components and applies the imaging condition to the decomposed angle components to form the angle gathers. Conventionally, the angle decomposition is performed in frequency domain or by wavefield from multiple time steps which are not convenient and efficient for time domain RTM. We propose an analytic equation to make the angle decomposition performed on snapshot from each time step of the time domain wave extrapolator. In addition, to make the angle domain imaging condition efficient, we propose an angle decomposition method based on matching pursuit. Numerical examples on synthetic and real data demonstrate the feasibility of the proposed method.