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).为了限定南海海槽（Nankai Trough）沉积物的剪切强度并探究其摩擦特性，我们对综合大洋钻探计划（Integrated Ocean Drilling Program, IODP）C0023站位采集的原状样品开展了X射线衍射（X-ray diffraction, XRD）测试与实验室速度阶跃摩擦（velocity-step friction, VSF）实验。XRD分析遵循Vogt等人（2002）的实验方法；VSF实验设置了两类应力条件：一是1.0~5.3 MPa的原位有效应力（Zhang等，2021），二是10 MPa的恒定应力，实验速度覆盖1.6 nm/s（代表板块构造驱动速率）至30 μm/s区间，实验在室温下采用GIESA RS5型直接剪切仪完成。通过XRD分析，我们获取了受试样品的矿物组成；通过VSF实验，我们得到了摩擦力、摩擦系数以及速率-状态摩擦（rate-and-state friction, RSF）参数。上述RSF参数借助MATLAB软件包RSFit3000（Skarbek与Savage，2019）计算得到。