The most important development in the processing of 3-C data in recent years is the realisation that layered, anisotropic effects must be taken into account in the processing of the horizontal components. The 1995 Blackfoot 3-C, 3-D survey was reprocessed to see what impact this previously neglected effect would have on the final image. Present methods for determining the effective Vp/Vs ratio, which controls the behavior of the anisotropic conversion-point binning process, depend on the existence of dipping events for the analysis. A fault that exists in the deep part of the southeast portion of the Blackfoot survey has enough structure associated with it to reliably indicate that the effective Vp/Vs ratio in this part of the image is about 70% of the vertical Vp/Vs ratio. This implies that far-offset traces were mis-stacked by about 200m (6.6 bins) in the original processing of this part of the CCP stack. It is more difficult to pick the effective Vp/Vs ratio in other parts of the stack in an objective manner because of the lack of dipping events.
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