The common reflection surface (CRS) method is used to enhance the signal-to-noise ratio in a stack. It can be applied directly to a stack or pre-stack, to common-offset gathers across offset and midpoint. CRS uses dip and azimuth information calculated from a stacked volume to determine the shape of reflection arrivals over which local planar mixing is applied to enhance those arrivals and suppress coherent noise such as ground roll.
When applied to data pre-stack, the CRS gathers are used for pre-stack time migration and in general produce a sharper, more continuous section with less noise. Pre-stack CRS gathers can be used for improved velocity analysis; the cleaner semblance gives better definition of the velocity function. CRS stacking followed by post-stack migration will yield an improved section over the standard migration.
The CRS technique has been successfully applied to several different datasets around New Zealand. Improvements in signal-to-noise in vintage datasets has proved popular with our clients. CRS can be applied to selected lines or the entire survey.
CRS example for shallow reflector in land data with CRS run prior to PSTM.
PSTM example of shallow land data.