X-ray diffraction measurements and velocity-step friction experiments on core samples from IODP Site C0023 in the Nankai Trough Subduction Zone, SW Japan

In order to constrain the shear strength and investigate the frictional properties of sediments from the Nankai Trough, we performed X-ray diffraction (XRD) measurements and laboratory velocity-step friction (VSF) experiments on intact samples recovered from IODP Site C0023. The XRD analyses followed the method of Vogt et al. (2002), while the VSF experiments were conducted under in-situ effective stress conditions ranging from 1.0 to 5.3 MPa (Zhang et al., 2021), or at a fixed stress of 10 MPa, at velocities ranging from 1.6 nm/s (representing plate tectonic driving rates) to 30 μm/s, using a GIESA RS5 direct shear apparatus at room temperature. From the XRD analyses, we obtained the mineral composition of the tested samples. From the VSF experiments, we obtained friction, friction coefficients, and rate- and state friction (RSF) parameters. The RSF parameters were calculated using the MATLAB software package RSFit3000 (Skarbek & Savage, 2019).