Quantitative 3D strain analysis in analogue experiments simulating tectonic deformation: Integration of X-ray computed tomography and digital volume correlation techniques

The combination of scaled analogue modelling experiments, material mechanics, X-ray computed tomography (XRCT) and new tomographic deformation monitoring techniques (DVC - Digital Volume Correlation) is a new powerful tool not only to examine the 3 dimensional structure and kinematic evolution of complex non-axial deformation structures in scaled analogue experiments, but to fully quantify the spatial strain distribution and complete strain history .

X-ray computed tomography analysis (XRCT) permits the non-destructive visualisation of the internal structure and kinematic evolution of scaled analogue experiments simulating tectonic deformation. Optical non-intrusive 2D strain and surface flow analysis (DIC - Digital Image Correlation) in analogue experiments represents enables the complete quantification of localised and distributed model deformation, is an important advance in quantitative physical modelling and helps to understand non-linear rock deformation processes. The simple combination of XRCT sectional image data of analogue experiments with 2D DIC only allows quantification of 2D displacement and strain components in section direction. This completely omits the potential of CT experiments for full 3D strain analysis in complex deformation structures during non-planar, triaxial deformation.

In this study, we apply digital volume correlation techniques (DVC) on XRCT scan data of “solid” analogue experiments to fully quantify the internal displacement and strain in all 3 dimensions over time. Our first results indicate that DVC on XRCT volume data can successfully be applied to quantify the 3D spatial and temporal patterns of strain accumulation inside analogue experiments. We demonstrate the potential of DVC and XRCT volume imaging of tectonic analogue experiments for 3D strain analysis of a contractional experiment simulating the evolution of a non-axial pop-up structure. Furthermore, we discuss various options for optimisation of granular materials, pattern generation, and data acquisition for increased resolution and accuracy of the strain results.

3-dimensional strain analysis in the experiment volume is of particular interest for geological and seismic interpretations of complex geological structures. The volume strain data enable the mechanical analysis of the large-scale and small-scale strain history of geological structures which is required for realistically constrained fracture simulations in reservoir characterisation, geothermal energy extraction, Carbon-storage.