论壳内韧性流层及其构造表现

DUCTILE FLOW LAYER WITHIN THE CRUST AND ITS STRUCTURAL APPEARANCE

地球物理探测表明,在上地壳之下有一不均匀分布的壳内低速层,中地壳之中还有一些局部的低速层。现代破坏性地震震源主要集中于10～15km深处,相当于这一低速层之顶部,处于脆韧性过渡带内。从岩石变形的角度看,这个低速层是一个壳内的韧性流变层,以发育近水平的韧性剪切带和褶叠层构造为其特征。它在纵向上和横向上都是不均一的,代表了地壳尺度的韧性剪切带,在地壳构造的演化中起着极重要的作用。

It is evident from geophysical researches on the configuration of crust that there is a heterogeneous Intracrustal low velocity layer under the upper crust and some local low ve- locity layers within the middle crust. The active catastrophic earthquake focuses are mainly located in 10～15 km depth. which corresponds to the depth of the top boLundary of the main low velocity layer under the upper crust and is 8 brittle-ductile transition zone. From the viewpoint of the behaviour of rock deformation, this low velocity layer is a intracrustal ductile flow layer characterized by the development of shallow dipping ductile shear zones and folded layering structure. It is heterogeneous both in the vertical and horizontal direc- tions. It is suggested that this is a crust-scale ductile shear zone. which has acted as an im- portant role in the evolution of crustal tectonics.