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

本研究以蛇纹岩变形实验为基础，探讨中深地震的发生机理。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，对蛇纹岩在稳定性和脱水条件下进行了恒排量试验。样品为三巴川变质带（样品A）和长崎变质岩（样品B）的长长辉长岩-蛇纹岩。结果如下：1)使用A样例，在所有条件下均产生故障。蛇纹石和细晶脱水相的制格择优取向分别在稳定和脱水条件下对断层生成起重要作用。2)对于样品B，我们目前只在稳定条件下进行实验。试样塑性变形，不产生故障。样品A和样品B结果的差异可能是由各样品组成的反长岩的形式，如板状和针状。我们获得了在1 Gpa和3GPa围压、450℃到700℃、2.0到2.4 × 10^-5/s应变速率下的力学数据。结果表明，在相同温度下，流动应力随围压的增大而增大，且流动应力的温度依赖性增大。流动应力随围压的变化可能是由于变形机制由佩尔机制转变为位错蠕变所致。

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.