Seismic expression of shear zones: Insights from 2-D point-spread-function based convolution modelling. (November 2020)

• Record Type: Journal Article
• Authors: Wrona, T.; Fossen, H.; Lecomte, I.; Eide, C.H.; Gawthorpe, R.L.
• Is Part Of: Journal of structural geology. Volume 140(2020)
• Publication Date: 2020-11
• Subjects: Geology, Structural -- Periodicals; Géomorphologie structurale -- Périodiques; Geology, Structural; Periodicals; 551.805
• DOI: 10.1016/j.jsg.2020.104121
• Languages: English
• ISSNs: 0191-8141

Abstract

Abstract: Shear zones are common strain localization structures in the middle and lower crust and play a major role during orogeny, transcurrent movements and rifting alike. Our understanding of crustal deformation depends on our ability to recognize and map shear zones in the subsurface, yet the exact signatures of shear zones in seismic reflection data are not well constrained. To advance our understanding, we simulate how three outcrop examples of shear zones (Holsnøy - Norway, Cap de Creus - Spain, Borborema - Brazil) would look in different types of seismic reflection data using 2-D point-spread-function (PSF)-based convolution modelling, where PSF is the elementary response of diffraction points in seismic imaging. We explore how geological properties (e.g. shear zone size and dip) and imaging effects (e.g. frequency, resolution, illumination) control the seismic signatures of shear zones. Our models show three consistent seismic characteristics of shear zones: (1) multiple, inclined reflections, (2) converging reflections, and (3) cross-cutting reflections that can help interpreters recognize these structures with confidence. Highlights: 2-D seismic images of three large-scale shear zones observed in the field. Dependency of seismic images on frequency, illumination, dip and aspect ratio. Typical features are: (1) inclined, (2) merging, and (3) cross-cutting reflections. Reflection junctions indicate shear zone kinematics. Findings will help interpreters identify and map shear zones in seismic reflection data.