Patent ID: 6865489

Claim:
A method for pre-stack migration of common offset seismic traces obtained from a subterranean region where the seismic velocity varies both laterally (with x) and vertically (with ), said method comprising the steps of: a) selecting seismic velocity functions v( ) at at least two lateral (x s ) locations (at least three locations for 3D application) in said subterranean region, the number of such locations being determined by the degree of lateral velocity variation; b) transforming said common offset seismic data traces from the space-time (x-t) domain to the wave number—frequency (k-ω) domain; c) calculating a travel time map for each x s location using the velocity function selected for such location; d) calculating for each travel time map from step (c) a corresponding map of τ as a function of wave number p, where ωτ is the phase shift in the k-ω domain corresponding to the migration time shift in the x-t domain; e) using the τ-maps to find τ (p) as a linear function of x with a certain slope at each depth ( ) in the subterranean region; f) forming the migrated image from said seismic traces in the ω-k domain using pre-stack time migration with k shifted by an amount equal to the τ slope from step (e) multiplied by ω; and g) reverse transforming said migrated image back to the space-time (x-t) domain.