3:00 PM - 3:15 PM
[SSS07-06] Numerical and experimental analyses for development of deformation structures in faults
Keywords:deformation structure, force chain, velocity distribution
During earthquakes, various kinds of deformation structures such as composite-planar fabrics are developed by fault motions. Many previous works have reported the dependency of development of composite-planar fabrics on displacement, normal pressure, and particle size. However, slip rate has not well discussed. Here, we conducted frictional experiments with 0.0002–1 m/s slip rates by using quartz sand samples and microstructure observations. We also numerically simulated relative motion of granular materials under shearing by using Discrete Element Method (DEM) with assumption of the same Inertial number to that of frictional experiments, and analyzed the numbers and mean degrees of force chains, probability function of normal forces acting on contacting points, distribution of particle velocities, and that of relative displacements between adjacent particles. Microstructure observations after frictional experiments exhibited Riedel, Y, and boundary shears and grains aligned parallel to the P foliation. No dependency of frictional coefficients and their changes with slip in all cases of slip rate was observed by numerical simulations. Particle velocities showed characteristic distribution particularly when friction coefficient decreased in several time steps. The magnitudes of particle velocities changed sharply at some height subparallel to shear direction. At last stage of shearing, the discontinuous structure developed near the bottom like boundary shear, often observed in gouges after frictional experiments. In conclusion, variations of frictional behaviors and formation of deformation structures may be explained by fundamental physical properties of particles under shearing.