Combined structure and velocity stacks via the tau–p transform

Abstract

ABSTRACTReflection and refraction data are normally processed with tools designed to deal specifically with either near‐ or far‐offset data. Furthermore, the refraction data normally require the picking of traveltimes prior to analysis. Here, an automatic processing algorithm has been developed to analyse wide‐angle multichannel streamer data without resorting to manual picking or traveltime tomography. Time–offset gathers are transformed to the tau–p domain and the resulting wavefield is downward continued to the depth–p domain from which a velocity model and stacked section are obtained. The algorithm inputs common‐depth‐point (CDP) gathers and produces a depth‐converted stacked section that includes velocity information. The inclusion of long‐offset multichannel streamer data within the tau–p transformation enhances the signal from high‐velocity refracted basalt arrivals. Downward continuation of the tau–p transformed wavefield to the depth–p domain allows the reflection and refraction components of the wavefield to be treated simultaneously. The high‐slowness depth–p wavefield provides the velocity model and the low‐slowness depth–p wavefield may be stacked to give structural information. The method is applied to data from the Faeroe Basin from which sub‐basalt velocity images are obtained that correlate with an independently derived P‐wave model from the line.