Clarification of generation mechanism of intermediate depth earthquake based on detonation experiment of serpentinite

本文旨在通过蛇纹岩变形实验研究中深源地震的发生机制。利用安装在广岛大学和加州大学滨江分校的三轴固体介质变形装置，对蛇纹岩在稳定和脱水条件下进行了恒速率位移试验。样品分别为三坝川变质带（样品A）和长崎变质岩（样品B）中的辉绿蛇纹岩。结果表明：1）以样本A为例，在所有条件下均产生故障。在稳定和脱水条件下，蛇纹石相和细粒脱水相的晶格择优取向对断层的形成起着重要作用。2）对于样品B，我们目前只在稳定条件下进行了实验。试样发生塑性变形，不产生断层。样品A和B之间的结果差异可能是由每个样品组成的叶蛇纹石的形式分别如板状和针状来解释的。我们在1GPa和3GPa的围压、450 ℃到700 ℃、2.0到2.4x10^-5/s的应变速率下获得了力学数据。结果表明，随着围压的增加，相同温度下的流变应力和流变应力的温度依赖性增大。流变应力随围压的变化可能是由于变形机制由Peierls机制转变为位错蠕变机制所致。

The purpose of this research was to investigate generation mechanism of intermediate depth earthquake based on deformation experiment of serpentinite. We conducted constant displacement rate tests of serpentinite under stability and dehydration conditions of it, by a triaxial solid medium deformation apparatus installed at Hiroshima University and University of California, Riverside. The samples were antigorite-serpentinite collected from Sanbagawa metamorphic belt (sample A) and Nagasaki metamorphic rock (sample B). The results are followings;1) Using sample A, faults are generated at all conditions. The making lattice preferred orientation of serpentine and fine grained dehydration phases plays the important role for fault generation at stability and dehydration conditions, respectively.2) Using sample B, we conducted the experiments only at stability conditions up to now. The samples deform plastically, not generate the fault. The discrepancy of results between samples A and B may be explained by the form of antigorite composed of each samples such as platy and needle, respectively. We obtained mechanical data under 1 Gpa and 3GPa confining pressures, 450 C to 700 C, and 2.0 to 2.4x10^-5/s of strain rate. The results indicate that flow stress at same temperature and temperature dependence of flow stress increase with an increasing confining pressure. The change of flow stress with confining pressure is probably attributed to change of deformation mechanism from Peierls mechanism to dislocation creep.