Statistical evaluation of anisotropic features embedded in the fault gouge

Despite various physio-chemical activities and complexity involved during the formation of fault gouge, it has been commonly observed that the microstructural characteristics indirectly indicates the major tectonic deformation and its consequences in the sense of geometrical analysis. This study presents the statistical investigation of internal structures embedded in fault gouges by using 3D x-ray computed tomographic images. First, the slicing plane method (SPM) quantitatively evaluates the anisotropic variation in x-ray attenuation numbers across imaginary slicing planes. The star volume method (SVD) allows inferring the preferred orientation of grains in gouges. The results of three directionally cored fault gouge specimens suggest that the maximum coefficient of variation from SPM is perpendicular to the fault plane implying that the dominant layered structures is parallel to the fault plane. The SVD reveals that the orientation of grains exists within 30 degrees of the fault plane. The observations made in this study are consistent with those in previous studies, further highlighting the feasibility of image-based analyses to understand the microstructural features of gouges.