Seismic Diffraction Imaging to Characterize Mass-Transport Complexes: Examples From the Gulf of Cadiz, South West Iberian Margin

摘要

Mass-transport complexes (MTCs) are often characterized by small-scale discontinuous internal structure, such as slide blocks, rough interfaces, faults, and truncated strata. Seismic images may not properly resolve such structure because seismic reflections are fundamentally limited in lateral resolution by the source bandwidth. The relatively weak seismic diffractions, instead, encode information on subwavelength-scale structure, with superior illumination. In this paper, we compare diffraction imaging to conventional, full-wavefield seismic imaging to characterize MTCs. We apply a seismic diffraction imaging workflow based on plane-wave destruction filters to two 2D marine multichannel seismic profiles from the Gulf of Cadiz. We observe that MTCs generate a large amount of diffracted energy relative to the unfailed confining sediments. The diffraction images show that some of this energy is localized along existing discontinuities imaged by the full-wavefield images. We demonstrate that, in combination with full-wavefield images, diffraction images can be utilized to better discriminate the lateral extent of MTCs, particularly for thin bodies. We suggest that diffraction images may be a more physically correct alternative to commonly used seismic discontinuity attributes derived from full-wavefield images. Finally, we outline an approach to utilize the out-of-plane diffractions generated by the 3D structure of MTCs, normally considered a nuisance in 2D seismic processing. We use a controlled synthetic test and a real-data example to show that under certain conditions these out-of-plane diffractions might be used to constrain the minimum width of MTCs from single 2D seismic profiles.