Coherent diffraction imaging for enhanced fault and fracture network characterization

Abstract

Abstract. Faults and fractures represent unique features of the solid Earth and are especially pervasive in the shallow crust. Aside from directly relating to crustal dynamics and the systematic assessment of associated risk, fault and fracture networks enable the efficient migration of fluids and therefore have a direct impact on concrete topics relevant to society, including climate-change-mitigating measures like CO2 sequestration or geothermal exploration and production. Due to their small-scale complexity, fault zones and fracture networks are typically poorly resolved, and their presence can often only be inferred indirectly in seismic and ground-penetrating radar (GPR) subsurface reconstructions. We suggest a largely data-driven framework for the direct imaging of these features by making use of the faint and still often underexplored diffracted portion of the wave field. Finding inspiration in the fields of optics and visual perception, we introduce two different conceptual pathways for coherent diffraction imaging and discuss respective advantages and disadvantages in different contexts of application. At the heart of both of these strategies lies the assessment of data coherence, for which a range of quantitative measures is introduced. To illustrate the versatility and effectiveness of the approach for high-resolution geophysical imaging, several seismic and GPR field data examples are presented, in which the diffracted wave field sheds new light on crustal features like fluvial channels, erosional surfaces, and intricate fault and fracture networks on land and in the marine environment.

Distribution of seismic scatterers in the San Jacinto Fault Zone, southeast of Anza, California, based on passive matrix imaging

“…Keeping the non-specular component in the analysis allows retrieving signatures of localized scatterers such as cracks or inclusions that lack lateral continuity. Imaging such features whose size is of the order and even smaller than the seismic wavelength contributes significantly to seismic interpretation [55]. Fault surfaces and zones with increased fractures density are non-specular objects for surface sensors [56].…”

Boulder Detection in the Shallow Sub‐Seafloor by Diffraction Imaging With Beamforming on Ultra‐High Resolution Seismic Data—A Feasibility Study

“…Conventional seismic reflection methods can also be used for object detection by imaging PD hyperbolas in 2D and 3D seismic data sets (Bull et al., 2005; Carbon Trust, 2020; Gutowski et al., 2008; Vardy et al., 2008). As diffractions are up to two orders of magnitude weaker than reflections (Khaidukov et al., 2004), and thus difficult to detect within high‐amplitude reflection energy, a number of dedicated diffraction imaging techniques utilize reflection‐suppression methods such as Radon transforms (Bansal & Imhof, 2016), eigenvector filters (Bansal & Imhof, 2016; Guigné et al., 2014), plane‐wave deconstruction filters (Fomel et al., 2007; Ford et al., 2021), or adaptive subtraction (Khaidukov et al., 2004; Preine et al., 2020; Schwarz, 2019; Schwarz & Gajewski, 2017; Schwarz & Krawczyk, 2020). After suppression, the diffractions can be imaged via migration (Bachrach & Reshef, 2016; Ford et al., 2021; Preine et al., 2020), Radon transforms (Karimpouli et al., 2015; Nowak & Imhof, 2004), or beamforming (Guigné et al., 2014).…”

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

“…Seismic diffraction imaging has been used to characterize a range of complex geological targets including faults, channels, pinchouts, rugose interfaces, karstic carbonate reservoirs, and fracture zones (Decker et al., 2015; Fomel et al., 2007; Reshef & Landa, 2009; Schwarz & Krawczyk, 2020). In this paper, we explore the potential of diffraction imaging to characterize the complex internal structure and external morphology of MTCs.…”

“…(a) (b) et al, 2015;Fomel et al, 2007;Reshef & Landa, 2009;Schwarz & Krawczyk, 2020). In this paper, we explore the potential of diffraction imaging to characterize the complex internal structure and external morphology of MTCs.…”