Cross-profile acquisition and cross-dip analysis for extracting 3D information from 2D surveys, a case study from the western Skellefte District, northern Sweden

Two nearly parallel seismic profiles were acquired in the Kristineberg area, located in the western part of the Skellefte ore district, in northern Sweden. A novel approach in the acquisition was that all shots from each profile were recorded onto both lines, resulting in a third CDP line halfway between the two profiles. The combination of geometry, acquisition parameters and geological complexity of the area required specific processing techniques to produce a stacked section that could be correlated with the two in-line processed seismic profiles. The processing sequence included a carefully designed frequency filter, optimized stack methods and pseudo 3D processing by applying cross-dip corrections. Due to the long offsets between the profiles, the resulting stacked section does not provide any information in the upper 1.2 s. Below 1.2 s, the upper crust shows a north-dipping event that correlates well with observations on the in-line data. Sub-horizontal reflectivity is also observed in the upper 4 s of the stack, similar to what is observed on the profile west of the cross-profile. Cross-dip analysis shows that the north-dipping event observed in all three profiles has a westerly dip component. Our study shows that additional information on the sub-surface may be obtained through cross-profile acquisition and processing.