Seismic data processing method and system for migration of seismic signals incorporating azimuthal variations in the velocity

Abstract

A method and system for seismic data processing utilizes azimuthal variations in the velocity of seismic signals. The system and method utilizes a plurality of seismic energy sources that are located at known positions at the surface of the earth. The seismic energy sources generate seismic signals that propagate downward into the earth. Some of the seismic signals are reflected and diffracted by various sub-surface layers and are returned to the surface of the earth. The returned seismic signals are received by a plurality of receivers. The method includes the step of determining the distance from an energy source to an image point. A fast travel time of the seismic signal from the energy source to the image point is determined, and a slow travel time of the seismic signal from the energy source to the image point is determined. The azimuth angle between the energy source and the surface location of the image point is calculated. A first travel time of the seismic signal traveling from the energy source to the image point is calculated. A second travel time of the seismic signal traveling from the image point to the seismic receiver is calculated. The total travel time is calculated by adding the first and second travel time. The amplitudes from the recorded signal at the total travel time are phase adjusted and added into the output image at the image point. The foregoing steps are repeated for a plurality of image points beneath the surface of the earth and the total travel time is calculated.