Method and system for correcting for offset-dependent directivity

Abstract

A method and computer system for correcting seismic signals in a seismic survey, sensed in horizontal and vertical directions at receiver locations, is disclosed. According to the disclosed method and system, the horizontal and vertical seismic signal traces are processed in prestack gathers, after normal move-out correction. For each reflection event indicated in the prestack gathers, a performance function is evaluated over a range of zero-offset directivity and directivity slope values, using the horizontal and vertical pressure wave components sensed at the receivers. The zero-offset directivity and directivity slope values that return the maximum performance function are stored in connection with the gather and the reflection event, as indicative of the zero-offset dip and offset-dependent directivity of the reflective surface corresponding to the reflected event. These zero-offset directivity and directivity slope values are then used to correct the traces, or generate a new trace, corresponding to the pressure wave signal that is in the true reflected wave ray direction, minimizing the component of the sensed pressure wave that is transverse to the longitudinal wave ray direction. Detection and analysis of pressure-to-shear wave conversion, as well as amplitude-versus-offset analysis, is then facilitated by the present invention.