南海、中印半岛及其邻近地区的地震活动及应力状态

SEISMICITY AND STRESS STATE IN THE SOUTH CHINA SEA, INDOCHINA AND THEIR VICINITY

研究了南海、中印半岛及邻区的地震分布,地震主要集中在板块的边界。此外,一些浅震主要集中在缅甸西部和中缅边界。研究了Benioff带的形态。在爪哇海沟、菲律宾海沟,两板块耦合得不好;在缅甸山弧、安达曼-尼科巴岛弧下,俯冲的印度板块向NNE运动。由震源机制解及断层运动推断,主压应力方向在缅泰西部为NNE,在南海为NNW或S-N,与板块相互作用密切相关。

The distribution of earthquakes from 1973 to 1982 in the South China Sea, Indochina and their vicinity was studied using the data from I.S.C. It was found that the earthquakes are mainly concentrated along the boundaries of plates. Beside that, some shallow earthquakes are distributed in the west part of Burma and along the boundary between Burma and China, with a few earthquakes occurring in the South China Sea. The features of Benioff zone along theboudaries between the Indian plate, Philippine Sea plate and Eurasian plate were studied. The plates are not coupled well under the Java trench and the Philippine trench. The subducting Indian plate under the Burmese mountain and, Andaman-Nicobar arc moves NNE. The fault plane solutions of earthquakes were studied using the first motions of P waves. The stress state on the subduction zones and within the area were deduced from the fault plane solutions and the fault movement. It was found that the direction of principal compression axis of stress is in the NNE direction in west parts of Burma and Thailand, and in the NNW or N-S direction in the South China Sea. It was also found that the stress state has close relation with the interaction between plates.