Filtering of overburden azimuthal anisotropy effects from 3D seismic survey signals

A digital computing system for correcting seismic survey for the effects of overburden azimuthal anisotropy, comprising:

• a memory for storing seismic trace data corresponding to seismic survey signals corresponding to acoustic energy detected at a plurality of locations of the surface of the earth after traveling through the earth and being reflected from one or more subsurface geological structures, the seismic trace data corresponding to a plurality of gathers of seismic traces representative of acoustic energy detected at the plurality of surface locations, each gather of seismic traces including seismic trace data collected over time corresponding to a plurality of offset distances and a plurality of azimuths, and having a common midpoint
• a graphics display output device;
• and
• a programmed computer, coupled to the memory and to the output device, for:
• retrieving, from the memory, seismic trace data corresponding to a selected gather of seismic traces;
• correcting the seismic trace data in the selected gather for normal moveout;
• decomposing the corrected seismic trace data to generate first and second coefficient series, the first coefficient series associated with travel time and the second coefficient series associated with azimuth;
• generating analytical traces of the first and second coefficient series;
• measuring the magnitude of a quadrature phase component of the second coefficient series relative to the first coefficient series;
• again correcting the corrected seismic trace data to reduce the magnitude of the quadrature phase component of the second coefficient series;
• and
• storing the again-corrected seismic trace data in the memory.