Granular Cascading Motion Governs Fault Behavior

This dataset accompanies the study “Granular cascading motion governs fault behavior” and provides high-resolution four-dimensional (3D + time) X-ray computed tomography (CT) observations of granular fault gouge subjected to ring-shear deformation under controlled normal stresses. The experiments were conducted using a custom-built in-situ CT ring-shear apparatus, enabling direct visualization of particle-scale structural evolution during shear. Glass bead assemblies with different initial grain-size distributions were sheared under two representative normal stress conditions (0.6 MPa and 4.0 MPa), corresponding to intact-grain and crushing-mediated regimes, respectively. Time-resolved CT scans were acquired after consolidation and at successive shear stages (20, 40, and 60 minutes), capturing the spatiotemporal evolution of particle migration, segregation, fragmentation, and contact reorganization. The reconstructed volumes were segmented to identify individual particles and classify them into discrete size groups. The sample was further partitioned into vertical layers and concentric annular regions to quantify spatial heterogeneity along axial and radial directions. The dataset includes particle-scale statistics such as particle counts, grain-size distributions, coordination number, and porosity, as well as derived metrics describing cascading motion, densification, and structural reorganization. These data form the quantitative basis for identifying two distinct micromechanical regimes: a reversible granular cascade sustaining stick–slip instability under low stress, and a fragmentation-driven, fines-dominated regime in which cascade renewal is suppressed through kinematic isolation of coarse-grain triggers. This dataset is intended to support reproducibility of the published results and to serve as a benchmark for developing and validating discrete-element and continuum models of granular fault mechanics. It may also be useful for broader studies of shear-induced particle breakage, granular segregation, and frictional instability in geomaterials.