青藏高原岩石圈多层构造应力场

青藏高原构造应力场可按岩石圈下层、多震层和浅层地壳区分为三层。除了震源机制解方法和井孔原地测量方法可分别用于推测多震层和浅层的应力状况外,还可根据下层塑性流动网络,采用平分网络共轭角的方法估计下层的应力方向。对比岩石圈下层与上层(多震层)的构造应力场,其结果表明: 由于板块边缘驱动力主要通过下层的网络状流动实现其远程传递,故在总体作用趋势上,上层的应力方向受控于下层;又由于高原靠近喜马拉雅驱动边界,部分驱动力直接沿上层传递,致使局部地区上、下层应力方向相差显著。

Multi-layer tectonic stress field in the lithosphere of the Qinghai-Tibet plateau

The tectonic stress field in the lithosphere is divided into three layers in the Qinghai Tibet plateau, i.e. the lower lithosphere, the seismogenic layer and the shallow curst. In addition to that stress directions in the upper two layers can be estimated respectively using the focal mechanism solution method or in situ measurement methods, the method bisecting conjugate angles of plastic flow belts is suggested to estimate those in the lower lithosphere in which two families of plastic flow belts intersect each other forming plastic flow network. The comparison between the tectonic stress fields in the lower lithosphere and the seismogenic layer indicates that the stress directions in the upper layer are identical with and controlled by those in the lower layer in general tendency because the long range transmission of plate boundary driving force carried out mainly by the netlike flow in the lower lithosphere, while the considerable differences between the upper and lower layers exist in some local areas near the Himalayan driving boundary, where a part of the driving force is transmitted directly along the upper layer.