Fault constitutive properties at high velocities and the earthquake initiating processes

故障内流程比通常认为的动态得多。地震断层运动时沿断层的滑动速率可达1m/s左右甚至更快，大地震时沿断层的总位移可达数米。沿着挖掘出的断层偶尔出现的伪岩表明，至少在某些地震中确实发生了摩擦熔化。因此，断层在高速和大位移下的摩擦特性对了解地震起震过程具有重要意义，但尚未得到系统的研究。传统的外观在断层位移量方面太有限，无法产生摩擦熔化，也无法模拟断层内部的热自然过程。1990年安装在东京大学地震研究所的高速旋转摩擦装置的实验表明，摩擦加热对断层机械特性的影响比滑移率等其他影响大一个数量级以上。本研究项目的主要任务是设计和建造用于研究水热条件下高速摩擦特性的第二个高速装置，并使用第一个装置进行附加实验。主要结果如下：(1)设计并制造了一种新型旋转剪切高速摩擦装置，该装置可以在环境水压至50 MPa、温度至500摄氏度的条件下产生从3毫米/年到近10米/秒的滑移率。试验成功，为研究热液条件下断层的高速摩擦性能，以及高温腐蚀环境下材料的摩擦磨损性能开辟了道路。(2)通过首台高速机实验，揭示了干辉长岩模拟断层的整体力学特性。(3)在干高速实验的基础上提出了地震起震过程的两阶段模型，这可能解释了地震静止的起源。少

Intrafault processes are far more dynamic than normally considered. The slip rate along a fault during seismic fault motion reaches about 1m/s or even faster and the total displacement along fault amounts to several meters for large earthquakes. Occasional occurrance of pseudotachylytes along exhumed faults indicates that frictional melting indeed occurs at least during some earthquakes. Thus, the frictional properties of faults at high velocities and under large displacements are quite significant to understand the earthquake initiating processes, but they have not been systematically studied. Conventional appearatuses are too limited in the amount of fault displacement to produce frictional melting and are unable to simulate thermally natural intrafault processes. Experiments using a high-velocity rotary friction apparatus, installed to Earthquake Research Insitute, University of Tokyo in 1990, has revealed that the effects of frictional heating on the mechanical properties of faults … More are larger than other effects such as slip rate by more than one order of magnitude. The main task of the present research project has been to design and build the second high velocity apparatus for studying high velocity frictional properties under hydrothermal conditions and to perform additional experiments using the first apparatus. The major results are as follows.(1) A new rotary-shear high velocity friction apparatus was designed and built and this can produce slip rates ranging from 3 mm/yr up to almost 10 m/s, at ambient water pressures to 50 MPa, and at temperatures to 500 degrees Centigrade. Tests were successful and the machine will open ways of studying not only high velocity frictional properties of faults under hydrothermal conditions, but also frictional and wear properties of materials under high-temperature corrosive environments.(2) Overall mechanical properties of simulated faults in dry gabbro have been revealed through experiments using the first high velocity machine.(3) Two-stage model for the earthquake initiating processes has been proposed based on the dry high velocity experiments, and this may account for the origin of seismic quiescence. Less