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本文根据活动断裂的错动方式、白垩-第三纪红层变形和破裂的组合关系等资料,利用赤平投影作图求出各观测点主应力(σ_1、σ_2和σ_3)的参数,并结合震源机制和地壳形变测量数据,着重描述了喜马拉雅运动以来的构造应力场。结果表明:长江三峡(及邻区)各构造区域内σ_1轴向随时空而变化。按照“弹性回跳理论”和“Baushinger效应”分析了现今应力场的这种变化与地震活动的关系。提出构造应力场σ_1轴的长期变化,可以作为板内弱震活动区(带)的一种构造标志。
According to the combination of active faults and the deformation and rupture of the Cretaceous-Tertiary red beds, the parameters of principal stress (σ_1, σ_2 and σ_3) at each observation point are obtained by using stereographic projection mapping. Combined with the source Mechanism and crustal deformation measurements highlighting the tectonic stress field since the Himalayan movement. The results show that the axial direction of σ_1 varies with time and space in each tectonic area of the Three Gorges (and its adjacent area). According to the theory of “elastic bounceback” and “Baushinger effect”, we analyze the relationship between this change of current stress field and seismic activity. The long-term variation of the σ_1 axis of the tectonic stress field is proposed, which can be used as a structural indicator of the active zone (zone) of weak earth in the plate.