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

本研究的目的是通过蛇纹岩的变形实验，探讨中深地震的孕育机制。利用安装在广岛大学和加州大学河滨分校的三轴固体介质变形仪，在蛇纹岩的稳定性和脱水条件下进行了蛇纹岩的恒速驱替试验。样品为产于三叶川变质带(A)和长崎变质岩(B)的反钙闪石-蛇纹岩。研究结果如下：1)利用样本A，在所有条件下都能产生故障。蛇纹石脱水相和细晶脱水相的晶格择优取向分别在稳定和脱水条件下对缺陷的产生起着重要作用。2)利用样品B，到目前为止，我们只在稳定条件下进行了实验。试件发生塑性变形，而不是产生断层。样品A和样品B之间的结果差异可能是由分别由板状和针状等样品组成的反辉石的形式造成的。在应变速率为450℃~700℃，应变速率为2.0~2.4×10~(-5)/S的条件下，分别获得了1 Gpa和3 Gpa围压下的力学数据。结果表明，相同温度下的流动应力以及流动应力的温度依赖性随围压的增大而增大。流动应力随围压的变化可能是变形机制由Peierls机制向位错蠕变转变的结果。

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.