Patent ID: 7400553

Claim:
A method of seismic imaging overhanging subsurface structures, comprising the steps of: initiating a seismic source to generate seismic waves in a geologic medium which refracts the waves such that the waves, which initially travel downward from the seismic source, turn to permit the seismic waves to contact and be reflected from surfaces beneath overhanging subsurface structures which reflect the refracted waves such that the reflected waves turns as the reflected seismic waves travel through the geological medium; performing a two-pass approach by down-/up-ward extrapolation for both source and receiver wave fields, during the first-pass downward extrapolation, the turning wave energy at each depth z is saved for the second-pass extrapolation, the second-pass extrapolation reconstructs the contribution from the turning wave thereby obtaining four volumes of wave field P SD (x,y,z,ω), P SU (x,y,z,ω),P RD (x,y,z,ω), and P RU (x,y,z,ω), where ω is frequency and the subscripts S and D indicate source and receiver side, D and U represent down-going and up-coming wave fields, respectively, and after applying the certain imaging condition to each source-receiver wave field pair, arriving at the following volumes: I DD ( x,y,z )=Σ ω P SD ( x,y,z, ω) P* RD ( x,y,z, ω) I UU ( x,y,z )=Σ ω P SU ( x,y,z, ω) P* RU ( x,y,z, ω) I DU ( x,y,z )=Σ ω P SD ( x,y,z, ω) P* RU ( x,y,z, ω)+Σ ω P SU ( x,y,z, ω) P* RD ( x,y,z, ω) where * indicates conjunction of complex data.