Abstract: Formed in Mesozoic-Cenozoic time, the Kuche depression on the south side of Tianshan and the Urumqi depression on the north side of Tianshan demonstrate striking similarities in geometry, kinematics and dynamics. However, the seismic activities, especially middle and large earthquakes show evident differences between the two depressions. This paper analyses the primary factors that cause the differences. They include: 1. the difference in deformation extent between the two depressions; 2. the difference in fine structure of gophysics between the two depressions; 3. the difference in the environment of geodynamics between the two depressions.

Key words: Kuche depression, Urumqi depression, Characteristics of Mesozoic-Cenozoic structure, Earthquake activity

摘要： 形成于中新生代的南天山库车山前坳陷带和北天山乌鲁木齐山前坳陷带表现出类似的几何学、运动学和动力学特征,即坳陷内都发育4排近东西向展布的逆断裂-背斜带;新生代(特别是第四纪以来)表现出强烈的由山体向盆地的逆冲活动;逆断裂-背斜带的形成、演化和发展都受控于统一的近南北向构造应力场。然而,南北两个山前坳陷在变形强度、地球物理细结构、地球动力学环境等方面存在着明显的不同。对这些不同点进行了讨论,认为正是这些不同点的存在,使得天山南北两侧山前坳陷内的现今地震活动性显示出不对称性,即南天山库车山前坳陷5级以上地震基本都分布在第3排(秋里塔格)逆断裂-背斜带上,而北天山乌鲁木齐山前坳陷5级以上地震基本都分布在坳陷南部准噶尔南缘断裂附近及其以南的天山内部。

关键词: 库车坳陷, 乌鲁木齐坳陷, 中新生代构造特征, 地震活动