Seismic expression of shear zones: Insights from 2-D point-spread-function based convolution modelling
Thilo Wrona, Haakon Fossen, Isabelle Lecomte, Christian Haug Eide, Robert L. Gawthorpe
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.