A study for the prediction of precursory slips based on the contact mechanics of asperities

本研究由以下三个项目组成。压痕实验。我们主要对铝、铜和黄铜等金属样品进行了一系列压痕划痕测试。我们发现，随着压头水平运动的开始，压头向试件渗透得更深，并且随着水平运动的进行，压头向上漂浮。用模型进行了模拟，模拟结果与观测结果吻合较好。我们关注的事实是，初始摩擦力总是略高于稳态时的摩擦力。这可能与静摩擦大于动摩擦这一事实有关。通过跨断层传播波检测前兆滑动的实验试验。利用东京大学研究实验室的双轴夹层式装置，我们进行了P波和S波在断层上传播的一系列粘滑实验。我们发现，传输波对故障的接触状态很敏感。随着剪应力的增大，透射波的幅度明显增大。但随着前兆滑移的发生，上升速率略有下降。这被解释为更换粗糙度接触器的影响。研究断层几何形状(凹凸体高度、凹凸体大小、间距等)影响的实验。在传输波上。弹性波在人造断层上传播。断层表面切割出不同宽度和深度的平行凹槽。我们发现，波的透过率仅由沟槽深度/宽度与波长之比决定。我们还建立了基于故障刚度的数学模型。该模型很好地解释了当波长比接触的粗糙度大小长4倍时的观测结果。

This study consists of the following three projects.1. Indentation experiment. We performed a series of indentation scratch tests mainly on metal samples, such as aluminum, copper, and brass. We found that the indenter penetrated deeper into the sample with the onset of horizontal movement of the indenter, and that it floated up with the progress of the horizontal movement. A simulation was performed with a model, which well agreed with the observation. We focused on the fact that the initial friction force was always slightly higher than the friction at steady state. This may correlate the fact that static friction is larger than the dynamic friction.2. An experimental trial to detect precursory slips by transmission waves across a fault. Using a biaxial sandwich type apparatus at ERI, the University of Tokyo, we performed a series of stick-slip experiments in which P- and S-waves were transmitted across the fault. We found that the transmitted waves are sensitive to the contact states of the fault. With the increase in shear stress, the amplitude of the transmitted waves significantly increased. However, the increasing rate was slightly decreased with the onset of the precursory slips. This is interpreted as the effects of the replacement of asperity contacts.3. An experiment to investigate the effects of fault geometry (asperity height, asperity size, spacing etc.) on the transmission waves. Elastic waves were transmitted across an artificial fault. Parallel grooves with various widths and depths were cut on the fault surfaces. We found that the transmissivity of the waves is solely determined by the ratio of the groove depth/width to wavelength. We have also made a mathematical model based on the stiffness of the fault. The model well explains the observation when the wavelength is 4 times longer than the size of contacting asperities.